Paleontology of Kentucky, by W.R. Jillson, 1931: Chapter Two, Ordovician Fauna

Sponge sublobate or of compressed branches, surface showing mouths of branching, more or less tortuous canals which curve outward from the center. A few oscula present, distinguished by their larger size and surrounded by radiating channels. Sponge skeleton between the canals of variable thickness, sometimes appearing nearly solid, at others of loosely interwoven spicules.

Sponge subramose, of cylindrical or compressed branches up to 30 mm. or more in width. Its general features are shown in the accompanying figures.

This species has its best development in the Mount Auburn of the southern Bluegrass, is common in the Oregonia and is locally common in the Fairmount and Waynesville.

Distinguished from H. subramosa by the relatively small apertures, (6-8 in 5 mm. instead of about 5) and the presence of oscula scattered over the surface at intervals of 8-20 mm.

Common in the Arnheim of the southern Bluegrass, also in the Mount Auburn at Burdett Knob (Garrard County). Foerste mentions its occurrence in the Liberty near Lebanon. The specimen figured is exceptionally large.

Sponge consisting of a hollow central body, circular or elliptical, with an opening on the summit, continuous radially with a number of downward curving, hollow, distally closed arms.

This species has from eight to twelve arms. In the figured specimen the diameter is about 23 cm., that of the central body 14½ cm., osculum 4½ cm., height, of collar about osculum 2-2½ cm. Length of arms 5½ cm.

This remarkable form is found in the Brannon of Franklin County where it is common at two localities, unknown elsewhere. The writer has a specimen from the Curdsville, possibly basal Hermitage, from a few miles east of Nicholasville along the West Hickman Fault zone. It is rather small, with seven arms, and noteworthy because of the unsilicified condition. This has made possible the preparation of sections showing the characteristic hexactinellid spicules which are represented by calcareous casts (see Pl. IV, fig. 2). A silicified specimen from the chert waste near Dix River Dam may come from the Curdsville also. Other species have been described from the Mt.Hope and Liberty.

This species was originally described under the generic designation of Strobilospongia. Its general features are shown in the accompanying figure. According to Beecher (1889 p. 15) the spicular structure "so far as observed" agrees with that of Brachiospongia.

The type is from the Brachiospongia bed (Brannon) on Benson Creek in Franklin County. Fragments of the basalia are quite common in the Brannon chert drift in the central Bluegrass, some coming from above in the Woodburn. The only locality where good specimens may be obtained so far as the writer knows, is on the farm of Dr. A. M. Peter in northern Fayette County.

Free, spheroidal characterized by a series of minute bifurcating canals radiating from the center and opening on the surface.

A very common species of the Trenton varying from 5-10 mm., in diameter. They are most common at the Brannon horizon.

Cylindrical or angulated stems, often fluted, and ranging in size to over ten feet in length and a foot in diameter. A central tube with cystose tabulae and a peripheral vescicular structure characterize the fossil. (Grabau and Shimer 1909 pp. 46, 47.)

Up to 6cm. in diameter, characterized by longitudinal, rounded ridges separated by broad shallow grooves. These are not always continuous and often show a spiral twist.

Characteristic of the basal Liberty. In southern Indiana it has also been identified from just above the Columnaria reef of the basal Saluda.

Distinguished by a nodulose surface, the nodes more or less irregularly distributed but tending toward an arrangement in somewhat spiral vertical rows. B. nodulifera intermedia (PI. XVI, fig. 1) is intcrmed ate in character.

An associate of B. undulata in the basal Liberty. It may be a synonym of B. nodulosa Billings.

"Coenosteum massive, of dense, thick horizontal and concentric discontinuous laminae, separated by very narrow interspaces. No radial pillars. Small vertical tubes penetrate the several laminae, connecting interlaminar spaces. No astrorhizae." (Grabau and Shimer 1909, p. 46).

This very common Ordovician species forms masses from a few inches in diameter up to three or four feet, the surface characteristically pustulose. The base is usually concave with irregular, concentrically wrinkled epitheca. In all specimens observed by the writer, other than those which had been silicified, the material was recrystallized.

This form, possibly including some which are specifically distinct, occurs at a number of horizons in the local Ordovician, including the uppermost Bensons (cc). Woodburn (r), Cynthiana (cc), Mount Auburn (c), Oregonia member of the Arnheim (c), and Liberty.

The principal character of Climacograptus is the peculiar geniculation of the thecae which, in their proximal part, are attached parallel to the axis thereby placing the aperture into a more or less deep transverse excavation between two successive thecae. (Ruedemann 1908, p. 400)

Rhabdosome long and narrow, characterized by the slender, whip-like sicular end, the very small overlap of the early thecae, and the aspect of the thecae in the mature part of the rhabdosome, their distal free parts standing out as a series of squares from the broad median part of the lateral face. A characteristic Eden species.

Corallum turbinate, often curved. Septa alternately long and short, the edges of the longer twisted together at the center. Tabulae few or absent. Tetrameral arrangement well shown externally with removal of epitheca.

Corallum several cm. in length characterized by the great depth of the calyx, extending nearly to the base of the coral. Septa relatively few, (60-74 in mature specimens) not twisted at the center, and with crennulated margins. Primary septa strong, with three pseudo-fosulae, and double cardinal fossula, divided by the cardinal septum.

Corallum straight or slightly curved with strong annulated epitheca. Length up to 10 cm., or more, diameter 2-4 cm., depth of calyx 1-1½ cm. Septa one hundred or more alternating in size, the larger strongly twisted at the center.

Common in the Liberty, also in the Blanchester member of the Waynesville of Ohio, Indiana and Northern Kentucky, and the Whitewater of Ohio and Indiana.

A small commonly attached species, usually occurring in clusters. Length 15-20 mm., septa 58-62, alternately large and small, strongly twisted at the center. Calyx deep. No fossula.

Range and distribution essentially the same as S. rusticum. Common also in the Saluda.

Corallum massive of prismatic contiguous corallites with more or less developed septa. Walls thin, imperforate. Tabulae numerous.

Distinguished from C. vacua by the smaller corallites (Foerste 1909 p. 313). Specimens from this lower horizon have coralites varying from 2-3 mm. to 3-4 mm. in diameter, a conspicuous feature being the great irregularity in size within the same corallum. This last feature may be diagnostic, tho a feature of the smaller coralla with the rapidly diverging corrallites.

Massive coralla attaining a diameter of several feet. Corallites hexagonal or pentagons, of unequal size, the larger averaging 4 mm. in diameter. Septa alternately large and small, the latter rudimentary, the former extending almost if not quite to the center, this feature characterizing the species. Twelve to 15 or more septa in each series. Tabulae spaced about 1 mm. apart.

Foerste's variety interventa from the Woodburn is distinguished by the great inequality in size of the corallites within the same corallum. (see above). It occurs also in the Cynthiana.

This species forms a conspicuous reef (Bardstown reef) in the basal Liberty. In Southern Indiana a similar reef occurs in the basal Saluda (Madison reef), another occurs in the basal Waynesville (Fisherville reef). It is occasionally found elsewhere in the Richmond.

An assocate of C. alveolata, distinguished by the meagre development of septa, which occur as sharp striae. Corallites usually about 4 mm. in diameter.

Corallum an incrusting layer about 2 mm. thick. Corallites polygonal, of about equal size, 4 in 5 mm. Septa 12, scarcely reaching half the distance to the center. In some associated specimens the septa are replaced by papillae giving the appearance of a Protarea incrusted by Labechia papillata.

P. richmondensis makes its appearance in the Clarksville member of the Waynesville in Ohio and is common in both Liberty and Whitewater. In Kentucky it is characteristic of the Liberty on both sides of the arch.

Septa well developed tho short. Mural pores large, arranged in vertical rows between the septa.

Corallum massive. Distributed between the normal corallites with diameter of 2-3 mm., a variable number of smaller corallites, their number determining the shape of the larger ones. Septa as strong vertical ridges extending only a short distance into the cavity, 20-24 in number. Mural pores oval, large, in rows between the septa, 5-6 in 5 mm., longitudinal interspaces less than half the greater diameter of the pore. Tabule thin, a tube diameter or less apart.

Common in and rather characteristic of the Liberty, also present occasionally at other Richmond horizons.

Massive coralla of long slender prismatic corallites, quadrangular or petaloid in section. Four primary septa and numerous tabulae.

Septa nearly reaching the center. Diameter of corallites about .04". (See below.)

This is the species commonly referred to as T. minus. It is distinguished from T. fibratum in the smaller size of the corallites which are described as 1/3-1/4 line in diameter, i. e. 0.02”-0.03”.

It is listed by Bassler as from the Richmond. Foerste notes it also in the Maysville. Measurements on specimens from the Waynesville and Liberty show them to have 3-4 corallites in 2 mm. There is considerable variation within the corallum and some of the larger measure 2½ in 2 mm. Specimens from the Cynthiana, Lexington, and Tyrone commonly measure 1½-2 in 2 mm., rarely the smaller individuals in a corallum as high as
3 in the same distance. No specimens from the Maysville were available. The finer tubed forms of the Richmond constitute the T. approximatum, the earlier coarser ones T. fibratum. Those of the Maysville are perhaps intermediate. A number of specimens labeled as coming from the upper Cincinnatian from Belk Island are of the coarse type, T. fibratum, measuring 1½-plus in 2 mm.

Crown subcylindrical, calyx small. Three radials transversely and more or less equally bisected, or compound, these being, in addition to the right posterior the right and left, anterior or sometimes the anterior in place of the latter. Anal tube delicate and straight, first tube plate resting on the shoulders of both posterior radial, but not further entering the cup. Arms irregularly dichotomous, somewhat divergent. Stem pentagonal, quinquepartite, with interradial sutures.

Calyx small, about 4 mm. in length and almost as wide. Arms about 15 mm. long. Basals pentagonal forming nearly one-third the height of the body. The species is characterized by the small size of the calyx compared with the column, which has a diameter almost half that of the calyx, and the irregularity in the arrangement of the plates of the arms.

Calyx about as in Heterocrinus. Arms heteronomous, with ten main branches, straight, rather closely abutting, composed of a continuous series of syzygies of two plates each, the epizygals giving off ramules. Stem round tripartite (Zittel 1918, p. 212).

Calyx small, a little longer than wide, tapering regularly from above to the column. Arms above their origin on the second or third costal simple and composed of a single series of plates. Calyx and arms together give a subcylindrical form often overlooked because of their resemblance to a group of small stems. Length about 5 mm.

A more robust species with the arm plates proportionately shorter and more wedge shaped. Length of calyx about 8 mm. and the whole crown about 50 mm.

Calyx often highly ornamented, brachials passing imperceptibly into the arm plates and the IBr into the disk. Radials and costals subequal, distichals 2-8 or more. Arms rarely branching above the second bifurcation. IBr. numerous enclosing suplementary anals which sometimes form a series, also numerous interdistichals and interpalmers. Anus excentric at the top of a small protuberance. Disk depressed hemispheric extending very slightly above the level of the arm bases, composed of minute plates irregularly arranged, decreasing in size toward the arms. Arms 10-20. Pinnules slender, closely arranged. Column usually round.

Calyx obconical, interradial and interdistichal spaces more or less flattened giving pentagonal or decagonal section. Surface ornamented by angular ridges, radiating from the center of each plate, those following the rays more prominent. Arms 20, simple. Costals and distichals two. Fairmount, Cincinnati region.

Distinguished from G. decadacylus by the more globose calyx, and second bifurcation of the rays in the free arms. Eight distichals in the calyx, and one to seven additional ones before bifurcation. Ridges less angular. Arms thinner.

Plano-convex or subequally biconvex Orthids, with pedicle valve the more convex, surface radially striated, and hinge line commonly shorter than greatest width of shell. Brachial valve with median groove. Teeth prominent, supporting lamellae produced forward circumscribing a rather short, suboval or sub-quadrate muscular area. Cardinal process prominent, continued as a median ridge separating the muscular impressions.

D. emacerata is a semi-elliptical or subquadrate, finely striated, thin shelled species. Typically width about 20 mm., length about 0.75 width. Anteriorly 16-17 striae in 5 mm. Pedicle valve depressed convex, brachial flat, with faintly developed sinus.

A species of the D. emacerata type, distinguished (Foerste 1909, p. 215) by the somewhat more robust growth, the pedicle valve distinctly though not strongly convex, the brachial valve though nearly flat, sufficiently convex toward the beak to make the shallow sinus fairly distinct. Radiating striae coarser and their fasciculate arrangement more evident. In average specimens from the Jessamine there are 14-16 striae in 5 mm., width 15-20 mm., length, 0.75-0.80 width. In some of the more robust individuals the dorsal sinus is quite distinct.

Very common in the Hermitage and Jessamine formations of the Lexington limestone.

A relatively small, rounded, and more coarsely striated species than the above. Pedicle valve quite convex, rounded or centrally ridged, brachial valve flattened, and in the more robust forms with a well developed median sinus. Hinge line distinctly shorter than greatest width of shell. Commonly 10-12 striae in 5 mm. along the anterior margin. Width 12-15 mm., length 0.8-0.85 width.

This is the characteristic Eden Dalmanella, ranging up into the Mt. Hope and basal Fairmount.

This species is a larger and more robust form than D. multisecta. Muscular impressions deep set. Dorsal sinus well marked. Striae variable in coarseness, measuring as low as 6 or 7 in 5 mm. along the anterior margin to twice that many. Width typically about 18mm., length about 0.8 width.

Cumings lists this species (1908, faunal chart) from as low as the upper part of the McMillan. It is common in the Arnheim and Waynesville.

Shell resupinate, the pedicle valve with well developed cardinal area. Surface radially striated. Fold and sinus well developed in most species. Teeth large, supported by thick lamellae which continue as strong ridges around a short, obcordate muscular area, which is divided by a median ridge. Diductors flabellate. Cardinal process elongate, simple. Shell impunctate except in the later species.

A species characterized by the relatively short hinge line, with greatest width at, or a little anterior to the middle. Fold and sinus inconspicuous, visible only when viewed anteriorly. Plications usually simple, strong, 4-6 in 5 mm., anteriorly, about 40 in all, and more closely spaced laterally. Width commonly 15-20 mm., length 0.75-0.80 width, convexity about 0.5 width.

H. frankfortensis is first introduced low in the Jessamine, recurring again near the top and has its best development in the Benson. Where the typical Woodburn is developed it is not common. It recurs again in the Cornishville member of the Perryville.

Hinge line approximating the greatest width of the shell. Area common to both valves, extending much higher on the pedicle. Brachial strongly and evenly convex with incurving beak. Sinus broad. Width 30-40 mm., length about 0.7 width.

The characters distinguishing this species from H. occidentalis as listed by Hall (1847, p. 128) are:
1. The stronger and more prominent striae which are more regularly bifurcating; 2. beak of the pedicle valve more elevated and acute giving a greater height to the cardinal area; 3. brachial valve without the central depression (a faint sinus developed in the umbonal region) ; and 4. sinus more abrupt and deeper, often accompanied by a corresponding elevation in the brachial valve.

Different, combinations of these characters are common. Characters 2 and 3 are not of great practical value, and of the remaining two, coarsely striated, shallowly sinuate forms are as common as deeply sinuated ones. If the two are to be separated it would seem to be desirable to limit the species to the medium to coarsely striated forms with deep sinus, the latter character being suggested in the name.

A finely striated H. occidentalis. In the original description it occupies an end position in the series with the coarsely striated H. sinuata at the other end and H. occidentalis between. Mention was also made of the absence of the dorsal groove.

About the same range as the preceding species, but more common in the Maysville.

A H. occidentalis with a distinct and broad median depression extending from the beak to the anterior margin of the brachial valve. In the types the hinge line is prolonged giving acute cardinal angles. For the associated form with rounded cardinal angles and hinge line less than greatest width of shell Foerste (1909, p. 224) has proposed the varietal designation richmondensis.

Shell small, subequally biconvex with greatest width at or a little anterior to the middle. Pedicle valve evenly convex, brachial marked by a prominent depression extending from the beak to the anterior margin. Surface marked by coarse bifurcating and trifurcating striae crossed by prominent lamellose lines of growth which are particularly conspicuous in the grooves between the striae and give the surface a sculptured appearance. Interior of pedicle valve with strong vascular markings. Width commonly 17-22 mm., length of hinge 0.75-0.80 width, length 0.80-0.85 width.

To this type of Hebertella Foerste (1914, p. 258) has applied the generic name of Glyptorthis.

H. insculpta occurs at several rather restricted horizons: a. base of the Blanchester division of the Waynesville; b. base of the Liberty (or top of the Waynesville); and, c. a zone 15'-20' above the base of the Liberty.

In Kentucky it is known from the base of the Liberty along the eastern area of outcrop as far south as Montgomery County.

Representatives of this genus corresponding in character to H. occidentalis, H. sinuata, and H. subjugata are common in the Cynthiana and basal Million. Two species have commonly been recognized. H. maria parkensis is a finely striated form with moderately developed sinus, essentially H. subjugata. H. latasulcata, (types from the Rogers Gap) has moderately coarse striae, and a broad shallow sinus, corresponding in character to H. occidentalis. The narrow muscle scar referred to by Foerste (1914, p. 131) in comparing H. latasulcata with H. occidentalis the writer does not believe to be characteristic of the Cynthiana species, and while the obcordate scar is better developed in the later forms, it is a feature of the larger individuals which are more common at the higher horizons. H. maria parkensis is also known from the Salvisa member of the Perryville.

A spiriferoid Orthid with long straight hingeline and strongly plicated biconvex shell. Brachial valve with strong median fold, pedicle valve with corresponding sinus. Cardinal area about equally developed on each valve. Hinge teeth thick and prominent.

On the basis of the development of the plications of the fold and sinus Cumings (1903, p. 40) has grouped the species into the uniplicable, biplicate, and triplicate groups. All species described below are included in the Triplicata which has been further subdivided by McEwan (1919, p. 390) into—

A. Low fold subgroup
P. colbiensis
P. precursor
P. clarksvillensis
P. acutilirata

B. Ponderosa subgroup
P. ponderosa
P. ponderosa auburnensis
P. preponderosa

C. High fold subgroup
P. laticosta
P. unicostata
P. cypha

A small Platystrophia with only moderately elevated and not strongly compressed fold and shallow sinus. Plications 4 on the fold, 3 in the sinus, subequal in size. Lateral plications 8-10. Hinge line usually a little less than greatest width of shell. Width 21-22 mm., length about 0.8 width. The Woodburn specimens average somewhat smaller.

Common in the Woodburn and Cynthiana (Greendale) of Central Kentucky, also in the Rogers Gap.

Shell transverse, with high, moderately compressed fold and deep sinus; cardinal angles seldom less than seventy degrees. Lateral slopes flatly-convex with 5-7 broad, angular plications. Fold with four, sinus three plications, the lateral ones much reduced. Width commonly around 30 mm., length, 0.6-0.7 width.

Common throughout the Maysville, typically developed in the Fairmount. Similar specimens are found in the Waynesville.

The characteristic features of P. cypha are the high compressed fold and deep sinus with a tendency toward the disappearance of the lateral plications leaving two prominent plications on the fold and one in the sinus. James’ type is a form with extended hinge. Such forms have from 10-12 plications on the lateral slopes. On the other extreme are forms with more or less rectangular cardinal angles and 6-8 plications laterally. A contrast with P. laticosta is one of the degree of compression of the fold and reduction of the lateral plications. An extreme is a form with the general contour of P. laticosta, i. e. more or less rectangular cardinal angles and 5-6 plications on the lateral slopes, but with the lateral plications almost or entirely obsolete. For this "uniplicate P. laticosta" from the Bellevue, Cumings has given the name P. unicostata.

Foerste has recognized the variety P. cypha conradi, (Arnheim), a shell with the prolonged hinge, numerous plications on the lateral slopes, and stronger lateral plications on the fold and sinus.

A species of the P. laticosta type but, with narrower and more numerous plications on the lateral slopes (7-9), the plications of the fold and sinus of more nearly equal size with the resulting relatively broader and less angular fold and sinus. The lateral slopes are somewhat fuller, giving less prominence to the fold.

Typical P. acutilirata is a strongly ventricose shell, characterized by a low, broad, rounded fold with four approximately equal plications, and numerous plications along the convex lateral slopes. There is every variation in hinge line from long, with spine-like cardinal extremities, to shorter than greatest width. The following varieties have been recognized:
var. prolongata—forms with spine-like cardinal extremities. The typical form of P. acutilirata has the very extended hinge and acute cardinal angles, but not spinelike; and var. senex—a gerontic form with greatly thickened shell, thickness often in excess of length and a tendency toward the more rectangular cardinal angle.

Liberty and Whitewater of Ohio and Indiana. The var. prolongata and var. senex are from the Whitewater.

Characterized by the large size, greatly thickened valves, and quadrangular outline. Fold prominent, though rounded, with usually four plications. Plications on the lateral slopes 7-9.

A variety with hinge line much shorter than greatest width of shell resulting in fewer plications on the lateral slopes (5 or 6) and a more globose form.

Very common in and characteristic of the Mount Auburn in the region around Cincinnati.

This species is based on specimens from the Catheys near Nashville, Tennessee. It is smaller than P. ponderosa and has a more compressed and elevated fold, these constituting the only differences. Greatest width 26-27 mm., width along hinge 24 mm., length 20 mm., thickness 20 mm.

Specimens of what may be this species were found at the top of a railroad cut about five miles southeast of Winchester on the Ruckersville road, just above the crinoidal limestone marking the introduction of abundant Plectambonites rugosus.

Resembles Orthis in the strong ribbing but differs in the comparatively low area of the pedicle valve and subequal bi-convexity. Compared with Hebertella it lacks the fold and sinus and the shell is not resupinate.

A small rounded, subequally biconvex Plectorthis with hinge area inconspicuous and not exceeding one third the width of the shell. Width 8-9 mm. Length about the same. Surface marked with about twenty simple plications.

A species in which the intercalation of the secondary plications begins within a few millimeters of the beak, others added anteriorly. These soon attain the strength of the primary plications giving a uniformly plicated shell. Width about 15 mm., length 0.65-0.80 width.

A species with typically simple primary plications though in the larger individuals there is usually a trace of secondary plications anteriorly. Width of average individual around 20 mm., length about 0.7 width.

Distinguished from P. plicatella by the addition of secondary plications at a distance of about 10 mm. from the beak. The primary plications remain more conspicuous to the anterior margin, where with the two or sometimes three secondaries a fasciculate arrangement is distinct. The postero-lateral plications tend to remain simple.

A shell distinguished from the preceding in that the secondary plications more nearly attain the strength of the primaries anteriorly.

These last three species characterize the Fairmount of southern Ohio and Indiana and adjoining parts of Kentucky.

A resupinate, impunctate shell with brachial valve convex, pedicle elevated at the umbo and becoming flat or gently concave anteriorly and laterally. Dental lamellae prominent, extended around the subquadrate muscular area. Cardinal process erect.

Shell subcircular to semi-elliptical, characterized by from twenty to thirty coarse, broadly rounded and widely spaced plications, suggestive of the Pelecypod genus Pecten. Width normally about 25-30 mm., length 0.8-0.9 width.

Of the D. subquadrata type differing in the following minor points (Foerste, A. F., 1909c, p. 320); 1. more conspicuous flattening of the pedicle valve; 2. a shallow sinus anterior on the pedicle valve of some specimens; 3. shell frequently wider posteriorly than across middle; 4. plications usually somewhat coarser; and, 5. muscular area of pedicle valve relatively smaller, occasionally less than half the length of the valve.

Characteristic of the upper Benson, recurring again in the Cornishville member of the Perryville.

Shell suboval to subquadrate, width 30-40 mm., length about 0.8 width. Characterized by the relatively large cardinal area of the pedicle valve which is strongly recurved anteriorly bringing the beak some distance anterior to the hinge line. Radiating striations rather coarse and rounded. Beak of the brachia] valve strongly incurved.

Characteristic of the Oregonia member of the Arnheim as far south as Nelson County on the west, and Mason and Lewis counties on the east.

A subquadrate form with hingeline a little less than greatest width of shell and sharply rounded cardinal angles. Brachial valve evenly convex with a shallow sinus which sometimes extends up on the umbo. Pedicle valve a little convex at the umbo, becoming flat or slightly concave anteriorly and laterally, with beak smaller and less incurved. Lateral striae curving strongly outward, some terminating on the cardinal margin.

Common in Liberty and Whitewater faunas. It is ordinarily introduced just above the upper Hebertella insculpta horizon.

A depressed plano-convex, transversely elliptical shell, with the general appearance of a Strophomenid but with open delthyrium. Surface striae fine. Pedicle valve convex, with large muscular impression extending anterior to the middle consisting of small adductors centrally situated and two greatly enlongate, flabellate diductors which do not unite in front. Cardinal process simple, prominent extended anteriorly as a median ridge through the muscular area. Shell substance punctate.

This genus is represented by a single species H. clytie Hall, from the lower Hermitage. Width about 30 mm., length 0.7-0.75 width.

Resupinate concavo-convex shells, essentially biconvex in the sinuate species. The species described below may be conveniently grouped as follows:

A. Sinuate biconvex forms. Sinus on pedicle valve, fold on brachial. S. millionensis, S. sinuata, S. sulcata;
B. muscular area of pedicle valve bordered by a distinct ridge, which is deflected anteriorly leaving a median gap. S. planumbona, S. vicina, S. nutans, S. planoconvexa, S. maysvillensis, and S. vetusta;
C. flabellate muscular area. S. incurvata. and S. neglecta; and,
D. muscle scar weakly delimited. S. hallie.

A rather large, semicircular, finely striated species. Cardinal angles 75-85 degrees. Muscular area of pedicle valve flabellate, with sharply raised border, deflected anteriorly leaving a gap. Radial markings extended beyond border. Interior of pedicle valve distinctly thickened along anterior and lateral margins. Length commonly 40-45 mm., width: length 4:3. Convexity of brachial valve 7-10 mm., in specimens 40 mm. wide.

Fenton (1928 Midland Naturalist Vol. XI, p. 147) abandons this species on the basis of Shepard's inadequate description and figures, and absence of the types.

Tyrone and Camp Nelson. Ulrich (1888, p. 108) also lists it from the Curdsville.

A semi-elliptical, finely striated shell of the S. planumbona type. Width 30-35 mm., length 0.6-0.7 width. Convexity of the brachial valve 4 or 5 mm. in the semi-elliptical and 6-7 mm. in the more quadrate forms.

Characteristic of two horizons in the Lexington limestone, the upper Benson and Cornishville. This type of shell is next known in the upper Arnheim where it re-appears as S. concordensis. (Foerste 1912, pp. 36, 37).

A small sinuate form distinguished from S. sulcata by the wider spaces between the radiating striae and relatively narrower shell. The striae are rather coarse, 4-6 in 2 mm. The largest specimen seen (Foerste) is 19 x 13.5 mm. Cardinal angles 80-90 degrees.

Base of the Eden from the vicinity of Million, Madison County Kentucky.

Small, subtriangular or subpentagonal, cardinal angles more or less rectangular. Brachial valve flattened posteriorly for 5-7 mm. then curving rapidly antero-laterally. Pedicle valve with a reversal of curvature near the middle resulting in a piano-, rather than concavo-convex shell. Striae moderately coarse, 4-5 in 2 mm. anteriorly. Width of larger individuals 27 mm., length, 0.85 width. Muscle scar of pedicle valve weakly delimited especially anteriorly.

In the Cincinnati area it is most common in the Southgate, though also present in the Economy. In Central Kentucky it ranges from just above the Rogers Gap beds to the base of the Garrard.

Closely related to S. planoconvexa. It is larger and proportionately longer, triangular or pentagonal in outline due to the downward deflection of the antero-lateral parts of the brachial valve. Convexity of the brachial valve distinctly greater in the longer forms. Width, 25-35 or 40 mm., length, 0.9 width. Convexity frequently 0.4 length. Cardinal angles more or less rectangular rounded in the older individuals.

S. maysvillensis is introduced in the Mt. Hope in Central Kentucky, has its best development, associated with Constellaria florida, in the basal Fairmount, and occasionally ranges as high as the Orthorhynchula horizon of the upper Fairmount. In north central Kentucky and adjoining parts of Indiana and Ohio there are two Strophomena horizons in the Maysville, a lower one in the basal Mt. Hope where S. maysvillensis is common, and a higher one characterized by S. planoconvexa in the basal Fairmount. S. hallie is regarded as a precursor.

Shell semi-elliptical, brachial valve moderately convex, pedicle valve but slightly concave giving a plano-convex shell. Striae coarse, 3-4 in 2 mm. near the anterior margin. Width 25-40 mm., length, 0.7 width. Convexity of brachial valve commonly not more than 6 mm., concavity of pedicle valve 1-2 mm. Foerste has suggested that the difference in form between S. maysvillensis and S. planoconvexa is one of environment. S. maysvillensis being merely the more healthy form.

Throughout Northern Kentucky and adjoining parts of Ohio and Indiana S. planoconvexa characterizes a zone in the basal Fairmount. Farther south it occurs higher and ranges to the top of the Fairmount.

A sinuate Strophomena distinguished from S. sulcata by its somewhat larger size and coarser striae. The deeper, narrower sinuses are more common in S. sulcata than in S. sinuata. Width often 25mm., length, 0.6-0.65 width. Striae about 2.5 in 2 mm.

Shell finely striated, quadrate. Brachial valve flattened 2/3 of the way anteriorly from the hinge. Muscular area of pedicle valve circular, deeply impressed, bordered by curved, sharply elevated ridges which are deflected forward producing an anterior gap. Shell distinctly thickened along the anterior and lateral margins, crossed by vascular grooves. Striae normally subequal or alternating in size, less frequently an alternation of one coarse with 2 or 3 fine ones. Width, 30 mm., length, 0.75 width, striae 5 in 2 mm.

In the Richmond areas of southern Ohio S. planumbona is introduced near the base of the Clarksville, more commonly as the variety elongata, the typical forms common in the upper Blanchester and Liberty. Southward in Kentucky on both east, and west flank it is limited to the uppermost Waynesville and Liberty.

Shell biconvex with fold on the brachial and sinus on the pedicle valve, semi-circular, with hinge line about equal to greatest width of shell. Muscular area of the pedicle valve about three-tenths the width of the valve, bounded posteriorly and laterally by a sharply elevated border which disappears anteriorly. Width, 18-23 mm., length 0.8 width. Striae about three in 2 mm.

S. sulcata has a vertical range from the Clarksville to the top of the Whitewater. In the Liberty-Whitewater it is represented in Kentucky as far south as Madison and Marion counties. In the Waynesville it is known from the Clarksville in Lewis County.

A strongly concavo-convex, finely striated species of the S. planumbona type with pentagonal outline. Margins of posterior half of shell only moderately divergent. Hinge occasionally a little extended. On the pedicle valve and anterior part of the brachial valve several fine striae alternate with a coarse one, posteriorly on the brachial valve the striae are coarser and subequal or alternating in size. Anterior and lateral margins of pedicle valve abruptly and strongly thickened on the interior, the thickened border crossed by strong vascular markings. Width, 20-30 mm., length 0.7-0.8 width. Foerste (1912, p. 70) regards the typical form as the retarded gerontic form of S. concordensis.

Associated with S. neglecta and S. vetusta precursor forming a conspicuous Strophomena zone with a vertical range of only a few feet in the middle Blanchester from Lewis County, Kentucky to southern Indiana.

A large, subquadrate, finely striated species with flabellate muscle area in the pedicle valve. Width, 40-45 mm., length, 0.75 width. Hinge often extended. Shell thin, rather evenly concavo-convex. Muscle area of the pedicle valve large, circular to elliptical, diameter about 2/5 the width of the shell. Lateral border sharply elevated but impressed area rises gradually anteriorly.

Restricted to the middle Blanchester. Along the eastern area of out-crop it is known as far south as Bath County. It is known in southern Indiana but has not been listed from the western area in Kentucky.

A large species often attaining a width of 40 mm., length, 0.7 width, with rectangular or slightly extended cardinal angles, and high cardinal area. Radiating striae very fine on the pedicle valve (18-21 in 5 mm.), much coarser (8-10 in 5 mm.) on the brachial valve. The presence on the pedicle valve of concentric wrinkles, growth lines, and the tendency of the striae to change their direction anteriorly and laterally gives a characteristic irregularity to the surface markings. Shell vertically wrinkled along the hinge line.

Middle Liberty to the top of the Whitewater (also Saluda). It is known in Kentucky as far south as Madison County in the east, and Nelson County in the west.

Concavo-convex striated shell with straight hinge line and well developed cardinal area. Pedicle valve convex with faintly delimited flabellate diductors enclosing elongate adductors. Cardinal process bilobed.

A common and variable species commonly around 40 mm. in width, length, 0.8 width. Cardinal angles rectangular to acute. Convexity variable. Striae alternating in size commonly one coarse to several fine ones.

A thin, fragile, flattened variety with length equalling or slightly exceeding width. Cardinal angles rectangular to slightly obtuse, lateral margins parallel or slightly convergent posteriorly. Width, 30-40 mm.

Similar to R. fracta in general contour but thicker and more convex and the shell averages a little smaller.

A large, massive variety with more deeply excavated muscle scars, and vascular markings and unusually large cardinal process. Width commonly 50-60 mm.

Common in the Bellevue at Cincinnati also in the upper Fairmount of the southern Bluegrass.

Distinguished from R. alternata by the nasute anterior outline. Width commonly around 40-50 mm. Length somewhat greater.

Concavo-convex, finely striated Strophomenids characterized by a conspicuous concentric wrinkling of the shell which is abruptly deflected anteriorly. Outline transversely subquadrate or semi-elliptical, hinge line forming greatest width. Muscle area of pedicle valve subcircular, with flabellate diductors. Cardinal process bifid. Interior of brachial valve prominently elevated at line of geniculation.

Shell transversely subquadrate with more or less extended cardinal extremities. Width, 25-40 mm. Length, 0.5 width. This species differs from the well known L. rhomboidalis with which it was formerly identified by the shallower and less numerous wrinkles and broader striations with narrower intervening grooves. The shell is relatively wider and in most specimens the top of the pedicle valve is relatively flat.

A common and characteristic Richmond species appearing in the Oregonia member of the Arnheim as the variety precursor which is distinguished by the less conspicuous wrinkling, smaller geniculation anteriorly and more convex pedicle valve. In Jefferson County Butts finds it in the Rhynchotrema dentata and Constellaria polystomella zones of the Arnheim.

Small, concavo-convex, very finely striated, transversely semi-elliptical Strophomenids. Hingeline forming greatest width of shell, cardinal extremities often acuminate. Cardinal process large, simple, occupying the partly closed delthyrium. Crural plates short giving rise to two septa.

A very small semi-circular, remarkably coarsely striated (plicated) species. Width about 5 mm., length, 0.5 width. Five striae occur in a space of 5 mm. The plicated appearance is characteristic.

A transversely, semi-circular, very finely striated shell. Width commonly 15-20 mm., length 0.5 width. Cardinal angles usually a little acuminate. A silky luster is a characteristic feature of the shell.

A very common species of the Eden. In Central Kentucky the introduction of this species in great numbers is regarded as marking the base of the Million. It is quite common at a horizon near the top of the Jessamine and again lower in the same formation. A somewhat larger form is characteristic of the Curdsville. It recurs again in the Richmond in the lower parts of the Clarksville and Blanchester divisions of the Waynesville, lower Liberty where it is very common, and again in the lower Whitewater.

Rostrate, thick shelled, strongly plicate shells, with well marked fold on the brachial, and sinus on the pedicle valve. Deltidial plates concave, thick. Teeth strong. Median septum of brachial valve extending more than one half the length of the shell, with the small cardinal process on its posterior extremity. Muscular impressions usually well defined. Beak of pedicle valve closely incurved over that of the brachial valve.

A small species with three plications in the sinus, four on the fold and 4-5 on either side. Length usually 10-15 mm., length:width = 1:1. It differs from R. capax chiefly in the small size, and more angular plications, fold, and sinus.

A characteristic species of the Lexington limestone with its best development in the Benson and higher formations, quite common also at various levels in the Jessamine. A small, more triangular form, H. trigonale is found in the Curdsville.

A species varying from rather thin, flattened forms in the younger individuals to highly ventricose forms with thickness often exceeding length. Beaks closely incurved. Plications 4 on the fold and 3 in the sinus. Growth lines prominent. In the younger individuals where the size is comparable to that of the average R. increbescens the thickness is proportionately much less and fold and sinus are shallow.

A characteristic Richmond species ranging from the base of the Liberty to the Whitewater.

A subtriangular species characterized by the development of two plications on the fold and one in the sinus. Width 12-15 mm., length, 0.9 width. Lateral plications 3-4.

A characteristic species of the Whitewater of Ohio and Indiana, occasionally found also in the Liberty. A variety R. dentatum arnheimensis Foerste is a characteristic member of the Oregonia fauna throughout its extent, also of the middle Arnheim (R. dentatum zone) as defined by Butts (1915, p. 42) in Jefferson County, Kentucky. According to Foerste (1909a, p. 228) it is distinguished by its usually larger size, more triangular and less globose outline, especially posteriorly, and the more angular plications. The majority of specimens seen by the writer from this horizon are relatively small.

A plicate Rhynchonelloid with the cardinal area extending about one third the width of the shell, shared by both halves, that of the pedicle valve being the higher.

The only described species is a subelliptical shell with the greatest width anterior to the middle. Pedicle valve with sinus, brachial with prominent fold. Four plications usually on the fold, three in the sinus, and about eight on either side. Width, 22 mm., length 0.9 width.

O. linneyi is found at three horizons in the local Ordovician, the Salvisa member of the Perryville, the Greendale member of the Cynthiana, and the upper Fairmount. Comparing specimens from these levels Foerste (1912, p. 133) states that the beaks of the Perryville forms are less incurved, that there is a tendency for the Fairmount forms to be more globose than those from the Cynthiana, and that there is a tendency among the Cynthiana individuals to increase the usual four plications on the fold to five or six.

A small, rostrate, sub-circular, biconvex, plicated, genus. Pedicle valve with median fold, brachial with sinus. Spirals with few coils, apex directed inward. Primary lamellae united by transverse jugum.

Distinguished from Z. modesta (Foerste 1914, p. 132) by the broader and shallower sinus within which the plications are subequal while in that species the central plication is distinctly larger than those on either side. A corresponding difference in the pedicle valve is the slightly more evident fold in Z. modesta and the median groove along it a little more evident.

A small species. Width, 9 mm., length, 8 mm., thickness 4 mm., with low median fold on the pedicle valve and sinus on the brachial. The sinus is occupied by about four plications and 7-9 occur on each lateral slope. The median groove on the fold of the pedicle valve is distinctly wider than the adjoining grooves and in the sinus the corresponding plication is comparatively stronger.

A comparatively large species with length, 8 or 9 to 14 mm., width, 1.2 length. It is distinguished from Z. modesta in addition to the larger size by the smaller number, hence coarser primary lateral plications (5-6 on each side), more common bifurcation of the lateral plications of fold and sinus and more prominent fold and sinus.

A large species attaining a length of 14-15 mm., distinguished from Z. cincinnatiensis by the greater number and smaller size of the plications.

Characteristic of the Waynesville of Oldham, Jefferson, etc., counties, also Clark and adjoining counties in the eastern area of outcrop.

Zoarium forming parasitic sheets giving rise to flabellate fronds. Apertures ovate with prominent lunaria. Mesopores numerous.

This is the only described species. It forms flabellate expansions from a few to 15 mm or more thick. Rounded monticules sometimes developed. Mesopores more or less isolating
the zooecia. Apertures round to oval, constricted posteriorly where a conspicuous hood shaped lunarium is developed.

Ramose hollow zoaria with oblique zooecial apertures. Lunaria hood-like. Mesopores abundant.

Distinguished from C. alternatum by the more robust growth, well marked maculae with subsolid centers (closed mesopores) surrounded by apertures somewhat larger than normal.

Zoarium of somewhat irregular, hollow or compressed branches, 2-5 mm. in diameter. Maculae absent. Zooecial aperatures in more or less regular diagonal series, about six in two millimeters.

Zoarium of small hollow contorted stems with prominent lunaria, giving the surface a rough appearance. In tangential section the lunarium is semicircular with its ends indenting the zooecial apertures.

Cystiphragms are developed in both (m)1 and (im). Particularly characteristic are the granulose wall structure and the small, usually numerous acanthopores, which lack the central lumen and concentric structure. Mesopores variable.

Zoarium massive to lobate, surface with conical or somewhat elongate monticules composed of zooecia slightly larger than normal. Mesopores few. Acanthopores small, numerous. Longitudinal section shows a succession of (m) and (im), the former characterized by the thickening of the walls and closer spacing of diaphragms.

A species distinguished from the preceding by its frondescent growth. It shows the same succession of (m) and (im).

Distinguished from M. mammulata by its mode of growth which is more discoidal with diameter up to 30 cm. and height about ½ diameter. Base concave with concentrically wrinkled epitheca. Mesopores more numerous. Acanthopores small, inconspicuous, appearing as small grannules, 2-3 to the zooecium.

Characteristic of the Whitewater. The writer has collected a similar Monticulipora from the Oregonia of Clark County which differs in the larger and more numerous acanthopores.

Cystiphragms are restricted to the (m) and mesopores are few or wanting. Bassler (1903 pp. 566-568) has grouped the described species as follows:
A. diaphragms present in the (m)
B. diaphragms absent in the (m)

Zoarium of smooth, compressed branches about one half cm. thick. Acanthopores small, 3-4 surrounding a zooecium. Mesopores absent except in the maculae. Diaphragms in both (m) and (im). Ten zooecia in two mm.

A tuberculated dendroid species with cylindrical or slightly compressed branches 5-15 mm. in diameter. It is distinguished from H. curvata by the absence of diaphragms and the slight crinkling of the zooecial walls in the (im).

Zoarium small, composed of cylindrical to subfrondescent branching stems 2-4 mm. in diameter. Surface smooth, zooecia direct, about nine in 2 mm. Mesopores moderately developed in maculae and elsewhere. Acanthopores small, variable in number, sometimes 8-10 around a zooecium.

Zoarium of smooth surfaced, branching fronds 3-5 mm. in thickness. Maculae not elevated but conspicuous because of great size of the zooecia. Mesopores few and restricted to the maculae. Zooecia thin-walled, direct. Acanthopores absent. Diaphragms 1- 1½ tube diameters apart in the (im), 4-5 times as numerous in the (m), associated with an increasingly crowded series of cystiphragms.

Zoarium of small cylindrical or flattened branches 4-5 mm. thick, with strongly tuberculed surface. Zooecia small, 10 in 2 mm. Acanthopores small, moderate in number. Diaphragms absent.

Common in the upper Arnheim (Constellaria polystomella zone) along the western side of the arch.

A strongly and sharply monticuled ramose species distinguished from H. bassleri by the more numerous acanthopores, presence of a moderate number of diaphragms in the (m) and in tangential section by the thick walled zooecial tubes with characteristic dotted or granular structure.

Characteristic of the Whitewater. The figured specimen is from the Oregonia from west of Lebanon in Marion County where it occurs in abundance. The writer cannot separate it from H. wortheni.

A species of Homotrypa is common in the light colored clay at the top of the Oregonia in Lincoln County, a ramose, slightly tuberculated form having the general appearance of H. richmondensis or H. cylindrica, and agreeing with the latter in many points of internal structure. The walls are much thickened in the (m) and the acanthopores are large and numerous occupying about one-third of the junction angles. In longitudinal section it differs in that the cystiphragms are limited to the early part of the (m), only occasionally occurring higher. In the (im) occasional diaphragms are developed and are present also associated with the cystiphragms in the (m) and continuing above them.

As originally described this species, referred to Homotrypella, forms rounded or compressed branches, 3-6 mm. thick and 2-12 mm. wide. Surface covered with small, conical monticules. Apertures polygonal, walls of only moderate thickness, and averaging 12 in 2 mm. Mesopores absent except in the monticules which are composed of zooecia slightly larger than the average. Acanthopores small, very numerous, three to five surrounding, and commonly indenting the apertures. Diaphragms widely spaced in the (im). Cystiphragms small, numerous in the (m), accompanied by an equal number of diaphragms. The types are from Pleasant Valley, Carlisle County.

Numerous specimens of a very similar form have been collected by the writer from exposures of the upper Cynthiana east of Winchester and other localities which differ from the species as described above in the more robust growth, attaining a thickness of 8 mm., and in the absence of acanthopores. The zooecia are a little smaller averaging about 10 in 2 mm. In spite of the difference in development of acanthopores the writer regards the two as specifically the same. In both the original specimens and in those just mentioned the meagre development of mesopores does not suggest the genus Homotrypella.

This species is exceptional for the genus in its massive, hemi-spherical form, commonly attached to brachiopod or other shells, and 2-4 cm. in diameter. Surface smooth or with maculae of larger apertures slightly elevated. Mesopores numerous, closely tabulated. Acanthopores numerous and strong. Cystiphragms line the zooecial tubes. In assigning this species to Homotrypella instead of Prasopora, only a very short region in the proximal end which is free of cystiphragms may be recognized as the (im). The difference in development of acanthopores is distinct.

Zoarium discoidal, composed of two or more superimposed layers, lower size concave, with wrinkled epitheca. Acanthopores small. Diaphragms usually wanting in the zooecia, close set in the mesopores.

A thin discoidal expansion about 2 cm. in diameter. Surface smooth with maculae of larger apertures. Diaphragms closely spaced in the mesopores. Cystiphragms lining the walls of the zooecia.

A small species about 5 mm. in diameter characterized by the eccentricity of the concentrically wrinkled epitheca.

Zoarium more or less hemispherical with concentrically wrinkled epitheca. Zooecia thin-walled and generally surrounded by angular mesopores. Acanthopores when present, never numerous or strong. The massive Monticuliporas differ in the granular acanthopores and wall structure.

Zoarium flattened discoidal to subconical, diameter normally 2-10 cm., base more or less concave. Zoarium occasionally lo-bate. Apertures subcircular, 7-8 in 2 mm., more or less in contact except at the junction angles. Maculae conspicuous, of larger apertures and more numerous mesopores. Acanthopores absent. Diaphragms closely spaced, about one-half tube diameter apart, accompanied by a series of cystiphragms lining the zooecial walls.

A common and characteristic form of the Hermitage and Jessamine, in the latter attaining the subconical form ("chocolate drop bryozoan"). Occasionally also in the Benson.

In the lower Cynthiana, particularly in the southern Bluegrass, occasionally also in the Brannon, there occurs a form differing from P. simulatrix in the discoidal form and presence of small acanthopores at many of the junction angles. In these respects it suggests the following species. Zoarium 4-8 cm. in diameter.

James based his species on specimens resembling small individuals of P. simulatrix, characterized by the presence of a conical, sharp pointed groove impressed on the wrinkled under surface. According to Bassler (1906, p. 48) this groove, representing the excavation left by the object (Hyolithes or tapering end of a cephalopod) upon which the colony grew, lacks systemmatic value. The species is distinguished by its smaller size (about 2 cm. in diameter), flatter form, weaker epitheca, and presence of small acanthopores.

Hermitage and Jessamine. In spite of the lack of systematic value of the basal groove the form it represents does have stratigraphic value.

Frond 2-6 mm. thick and 10 or more cm. high, more or less undulating and branching. Apertures circular, 7-8 in 2 mm. Mesopores numerous, occupying the relatively wide interspaces. Acanthopores small, numerous. Maculae conspicuous, of larger apertures, often with a central cluster of mesopores. Cystiphragms lining the zooecial tubes, accompanied by a smaller number of diaphragms.

Distinguished from P. vera by the fewer mesopores, correspondingly narrower interspaces, and smaller apertures. The zoarium in some specimens is almost massive.
Common through the Maysville and Richmond.

A form closely related to P. vera and P. decipiens. According to Nickles the zooecia are smaller than in P. vera. Zoarium commonly 1-3 mm. thick. Eight zooecia occur in 2 mm. Acanthopores numerous, often inflecting the zooecial walls, from 2-5 surrounding each aperture. The writer is not certain that he can separate it from these later forms.

A very common fossil of the Cynthiana, occuring in great numbers in the lower part (Greendale), common also in the Brannon.

Zoarium frondescent; acanthopores small. Mesopores generally abundant; diaphragms numerous.

A large frondescent species distinguished from H. frondosa by the smaller zooecia (10 in 2 mm.), smaller and generally fewer acanthopores, and fewer mesopores. Surface smooth, or with slightly raised maculae.

Zoarium large, frondescent, surface with small, sharp monticules at 3 mm. intervals. Zooecia moderately thick-walled, polygonal to circular. Mesopores abundant, rather uniformly distributed. Zooecial walls much thickened in the deep (m). Diaphragms absent in the (im), moderately to very abundant in the (m). Acanthopores fairly numerous, of small size with occasionally a larger one.

Ramose or frondescent bryozoa distinguished from Heterotrypa by the development of two sets of acanthopores, large and small.

Zoarium ramose to subfrondescent, 5-10 mm. in diameter. Surface smooth to sharply monticulated, maculae of larger zooecia and mesopores. Zooecia rounded, 7-8 in 2 mm. Mesopores abundant. Acanthopores fairly numerous, of two sizes. Diaphragms few to absent in the axial region, ½-2 diameters, apart in the periphery, closely set in the mesopores.

A characteristic fossil of the McMicken member of the Eden, ranging from the Southgate to the Fairmount.

Zoarium dendroid, branches compressed, dividing frequently and rather irregularly, from 4-10 mm. in width. Surface smooth, or with low, rounded monticules 2.5 mm. apart; occupied by clusters of cells a little larger than the average, with occasionally a few mesopores at their summits. Apertures sub-angular, about, 9 in 2 mm. Interspaces rather thick. Acanthopores large and prominent, when preserved, about 6 or 7 in 3 mm. Zooecia with thin slightly flexuous walls in the axial region and with diaphragms 2-4 times their diameter apart. As they curve gently into the (m), the walls thicken, and diaphragms become much more numerous. (Nickles 1905, p. 42)

According to Nickles, from the Lexington series associated with M. multitabulata and P. simulatrix. This indicates the Jessamine.

A flabellate Dekayella from 5-10 mm. thick. Zooecia angular, about 8 in 2 mm. Mesopores few, somewhat variable. Diaphragms remote in the axial region, 1½-3 to the tube diameter in the periphery. Large acanthopores about 2/5 as numerous as the zooecia, small set several times as numerous, sometimes obsolete in the older specimens.

Described as from the Lexington limestone, later referred to the Cynthiana (Bassler 1915), Lexington, Kentucky.

The type consists of the basal part of a ramose or sub-frondescent zoarium 2 cm. thick, branching, and with a rounded celluliferous base. Surface with low monticules consisting of zooecia larger than normal. Zooecia thin-walled, sometimes crinkled, in the (im), turning fairly abruptly into the (m) which is 2-3 mm. thick. Diaphragms few to absent in the (im) but occasionally a cluster of diaphragms 1-3 diameter apart occurs, in the (m) 1/3-1/2 diameter apart. The inverted V structure and hollow central tube of the acanthopores distinct. In tangential section the zooecia are relatively thin-walled, polygonal, 10 in 2 mm. Mesopores practically restricted to the maculae. Acanthopores of two sizes, the larger about 2/3 as numerous as the zooecia, frequently 2/5 the size of the zooecial tubes. The smaller ones are much more numerous, but in the greater part of the sections could not be detected.

The species is characterized by the rounded base of the zoarium and its large size. Other features are much like those of D. foliacea. The acanthopores are more numerous and the zooecia smaller. Surface features are essentially as in Heterotrypa parvulipora.

Distinguished from Heterotrypa in the single set of large acanthopores, and more meagre development of diaphragms in the periphery.

Zoarium ramose 6-10 mm. in diameter, characterized by the very large acanthopores, conspicuous externally as small spines. Surface more or less smooth, with maculae of larger cells and mesopores. Mesopores lacking except, in the maculae. Zooecia polygonal, 10 in 2 mm. Diaphragms absent in the (im), and few to absent in the (m).

The species ranges from the McMicken to the Fairmount, and is especially characteristic of the latter horizon.

Massive Heterotrypids with thin-walled, prismatic zooecia. Diaphragms and acanthopores well developed. Mesopores wanting.

Zoarium of thick undulating to subspherical masses. Zooecia thin-walled 9-10 in 2 mm., with comparatively large acanthopores averaging about one to the zooecium. Surface usually with small sharp monticules. Diaphragms wanting in the (im), one to two diameters apart in the (m). It is characterized by the monticuled surface, small zooecia, few acanthopores and absence of diaphragms in the (im).

Common in the upper Benson, also in the Cornishville and Cynthiana formations of Central Kentucky.

Subspherical to massive zoaria. Surface smooth or with maculae of larger zooecia slightly elevated. Zooecia 9-10 in 2 mm. Acanthopores large, occupying almost all junction angles. Diaphragms widely spaced in the (im), one to two diameters apart in the (m). The (m) recurs at successive levels in the zooecial tubes.

Common in the Waynesville, especially the lower part along the western side of the arch, also along the eastern from Montgomery County north. Common also in the Oregonia member of the Arnheim of the southern Bluegrass.

Zoarium variable. Characterized by the periodic thickening of the walls of the zooecial tubes, the development of acanthopores in these zones, and the meagre development of diaphragms.

Zoarium an expansion loosely incrusting crinoid stems, in size up to 60 mm. in diameter. It is characterized by its zoarial habit, the practical absence of mesopores, thin-walled prismatic zooecia, acanthopores of fair size in the periodic zones but small or absent elsewhere, and the almost complete absence of diaphragms.

Dendroid or frondescent zoaria with depressed stellate maculae, the interray spaces occupied by raised clusters of zooecia. Mesopores chiefly in the maculae, with gradually crowding diaphragms.

Characterized by its mode of growth, consisting of rigid cylindrical to subcylindrical stems 5-10 mm. in diameter bifurcating at regular intervals, seldom less than 50 mm. Diaphragms are more abundant in the (m) than in C. florida, and in the (im) are 2-3 tube diameters apart.

Zoarium ramose or subfrondescent, 3-5 mm. thick, with con-spicuous stellate maculae spaced at intervals of about 2½ mm., consisting chiefly of angular mesopores, commonly closed at the surface, and largest near the center of the cluster. In between the rays are groups of 5-15 zooecia compactly wedged together and forming conspicuously elevated radial ridges. These often coalesce to form more or less continuous transverse ridges. In shallow sections innumerable minute acanthopore-like structures are present in the zooecial walls and secondary material closing the mesopores. Diaphragms few in the zooecia, practically wanting in the (im). Mesopores closely tabulated, increasingly so as the surface is approached, the diaphragms occurring at the same level in adjoining tubes.

Common in and characteristic of the Fairview formation, also present in the Greendale division of the Cynthiana. A variety C. florida prominens Ulrich with monticules about twice the normal size occurs in the McMicken member of the Eden and the Fairview.

This species agrees with C. florida in all internal characters but differs in the dwarfed growth and the more sharply and more narrowly rayed maculae.
"The usual growth obtaining in C. florida is of rather broad, flat branches, seldom less than 10 mm. in breadth and 3 or 4 mm. in thickness dividing rather regularly at intervals of several centimeters. C. florida emaciata, however, is dwarfed in growth, the branches being usually rounded and from 3 to 5 mm. in diameter but sometimes reaching a breadth of 6 or 7 mm. Division occurred at short, irregular intervals, and an entire zoarium consisted of a small clump of closely interwoven narrow branches instead of a rather broad expansion as in C. florida"
(Ulrich and Bassler, 1904a, p. 38).

Common in the Cynthiana of Central Kentucky. A single specimen was found in the upper Benson. Many individuals of C. florida from the Fairview are similar.

Zoarium frondescent, sometimes of small flattened branches. Surface usually smooth but sometimes slightly monticulated. It is distinguished from C. florida by the much smaller and more closely spaced maculae which are two or three times as numerous within a given area, commonly not elevated, and by the nature of the maculae. The zooecia in the interray spaces are not wedged together but are more or less separated by mesopores. When the zoarium is monticuled it is the maculae (mesopores) that are elevated.

A smooth surfaced, ramose or subramose species usually 5-10 or more mm. in diameter with stellate maculae essentially as in C. florida but, without the elevated clusters of zooecia in the interrays. Maculae on the same level with or slightly depressed below the general surface.

Common at various horizons in the Richmond from the Waynesville to the Whitewater. A similar form occurs in the Cynthiana.

A species resembling C. florida, distinguished by the more f'rondescent growth, the numerous diaphragms in the (im) (1-1½ tube diameters apart) and the nature of the "stars." According to Nicholson (1875, p. 215)
"the different stars are definitely bounded .... .and appear to occupy definite polygonal areas, whilst in the former no line of demarcation can be detected between the different stars other than that afforded by the outer terminations of the elevated ridges. Each star is (in the best preserved portions of the coral) circumscribed and separated from adjacent stars by a distinct hexagonal border which has no great width and is occupied solely by the coenenchymal tubuli and not by the ordinary corallites."
The writer has been unable to use this latter feature with the numerous specimens from the Arnheim and some from the Waynesville.

Zoarium ramose, with more or less oblique, thick-walled zooecia. Diaphragms most numerous in the early portion of the short (m). Acanthopores small, few or wanting. Mesopores variable.

This species, commonly known as E. mutabilis Ulrich consists of smooth, cylindrical, infrequently dividing branches. Zooecia more or less oblique with thick interspaces. In the younger specimens the apertures are drawn out anteriorly, in the older, the zooecia are more direct and the apertures sub-circular. Maculae present. Mesopores variable. Acanthopores represented by dark spots at the junction angles. The zooecial tubes curve gradually toward the surface. Diaphragms about 2 diameters apart in the (im) and about 1 D. apart in the (m).

The chief feature is in the nature of the zoarium which forms smooth cylindrical branching stems 3-10 mm. in diameter with a rounded or pointed base. Zooecia rather thick-walled, oblique, with oval apertures in the more slender zoaria, about 7 in 2 mm. Acanthopores absent. Mesopores few. Diaphragms particularly common in the early part of the (m).

Common in and characteristic of the Cynthiana. An earlier though not common occurrence, is in the Brannon.

Zoarium of smooth slender branches, with small oblique zooecia, the apertures narrowing above and with channeled interspaces. Mesopores and diaphragms few or wanting. Acanthopores never numerous.

Cumings and Galloway (1913, p. 61) recognize two groups within the genus; B. arctipora group—characterized by delicate zoaria, rather large zooecia and scarcity of diaphragms and acanthopores; and, B. gracilis group—characterized by larger zoaria and conspicuous acanthopores.

A slender ramose species, 1-2 mm. in diameter, with oblique apertures which are attenuated above. These are arranged in obscurely longitudinal alternating series. The borders are distinctly marked off by impressed lines.

Zoarium dendroid, of smooth cylindrical branches 2-3 mm. in diameter. Zooecia small, about ten in 2 mm., opening obliquely on the surface with circular or elliptical apertures between which occur a moderate number of minute more or less circular mesopores. Small acanthopores present. Walls very thick and completely amalgamated in the (m). A few diaphragms occur in the (m).

Distinguished from B. gracilis in the more robust zoarium (6-10 mm.) and consequently less oblique apertures.

A very slender form with characters essentially as in B. gracilis but of smaller size and lacking diaphragms and mesopores. Zooecia emerge very obliquely with oval apertures measuring about 8 in 2 mm. longitudinally.

Zoarium ramose, discoidal, or massive. Zooecia prismatic. Acanthopores variable. Diaphragms often quite irregular, oblique or curved.

Zoarium ramose, 5-10 mm. in diameter. Maculae composed of larger zooecial apertures and some mesopores, sometimes a little elevated. Diaphragms few in the (im), about a half-tube diameter apart in the (m). Zooecia polygonal with numerous small acanthopores inflecting1 the zooecial walls.

Common in the McMicken and Fairview. Nickles recognized the Mt. Hope as the A. septosa zone.

A massive species 25-100 mm. in diameter and 2/3-3/4 as high. Surface monticulated. Zooecia thin walled, polygonal, 9 in 2 mm. Acanthopores small, numerous. Longitudinal sections show alternating zones of (m) and (im), with diaphragms one to two diameters apart in the (im), and one half to one third diameters apart in the (m).

Zoarium dendroid, of smooth cylindrical stems 10-12 mm. in diameter. Maculae conspicuous at intervals of 3-4 mm. composed of larger apertures. Zooecia thin-walled, polygonal, 7-8 in 2 mm. Mesopores absent. Zooecia curving uniformly toward the surface, with diaphragms never numerous in the (im), and closely spaced in the (m). Here they frequently simulate cystiphragms. The nature of the tangential section varies with the age of the specimen and depth of the cut. In a shallow section of a robust individual the wall is typically amalgamate and about 2/5 the diameter of the aperture in thickness, has a well marked cingulum, and acanthopores are but feebly shown. A little deeper, or in younger individuals, the cingulum disappears, small acanthopores become conspicuous at the junction angles with a row of very small ill-defined ones in between, 2-4 to each side of the aperture, giving a granular appearance to the wall. With greater depth these minute acanthopores disappear and the sharp black line of the integrate wall becomes distinct. Diameter of the normal zooecium about 0.25 mm.

This species is listed from the Bellevue around Cincinnati. It is very common in the Mount Auburn, again in the Sunset of the southern Bluegrass.

Ramose forms with the zooecial tubes rhombic or quadrate in cross-section in the (im). Acanthopores usually wanting.

Zoarium ramose to lobate, diameter of branches 4-10 mm. Surface smooth or with maculae of larger apertures slightly elevated. Acanthopores commonly described as absent but distinct rounded clear spots occur at the junction angles. Diaphragms few in the (im), closely spaced in the (m). Mesopores absent. Seven-eight zooecia occur in 2 mm. The characteristic rhombic zooecia may be seen in deep tangential sections or the weathered tips of the branches.

A smaller ramose form than the preceding species with diameter 2-3 mm., characterized by the development of mesopores. Ulrich and Bassler (1904, p. 45) have pointed out that the "mesopores" are inter-zooecial spaces instead of tubes with walls of their own.

Zoarium ramose. Diaphragms closely spaced in the tapering proximal end of the zooecia, few or wanting in the rest of the (im), crowded again in the (m). Closely tabulated mesopores more or less abundant.

Zoarium of dendroid branches 7-8 mm. in diameter, with strongly elevated more or less conical monticules occupied by zooecia of about normal size. Zooecia thin-walled, direct. Mesopores few. Diaphragms abundant throughout the zooecial tubes, about 1 diameter apart in the (im) and several times as abundant in the (m).

Zoarium dendroid, branches 1.5-2 mm. in diameter, frequently anastomosing. Surface smooth or with inconspicuous monticules. Zooecia thin-walled, apertures oval, 5-6 in 2 mm. Mesopores small, angular, abundant. Diaphragms moderately numerous in the proximal end, and closely spaced in the (m).

A recurrence of this species or closely related form in large numbers is found in the light colored clay at the top of the Oregonia. Cumings and Galloway (1913 faunal chart) show such an occurrence in the Tanner's Creek section in the Corryville-Arnheim and Waynesville.

Distinguished from H. ramosa by its more slender zoarium and smaller monticules.

Zoarium dendroid, 3-8 mm. in diameter, with prominent conical monticules several mm. apart which are characterized by the more numerous mesopores. Mesopores small, angular, abundant, in some cases completely isolating the zooecia.

Particularly characteristic of the McMillan but ranging down in the upper Fairview.

Distinguished from H. ramosa by the transversely elongate monticules often forming discontinuous ridges.

Zoarium ramose 6-12 mm. in diameter. Surface typically with low rounded monticules composed of larger apertures and more numerous mesopores. Zooecia about 7 in 2 mm. surrounded by a variable number of angular or subcircular mesopores. Tabulation of zooecia variable.

Zoarium dendroid, 6-12 mm. in diameter. Surface with low rounded monticules composed of apertures larger than normal and more numerous mesopores. Zooecial apertures circular, surrounded by a variable number of mesopores. Diaphragms numerous only in the proximal end of tubes, rare or absent above. Cumings (1908 p. 797) notes considerable variation in the tabulation.

Zoarium irregularly ramose. Acanthopores usually large and numerous. Mesopores variable. Zooecia much thickened in the (m), in section appearing ring-like.

Zoarium dendroid, the branches irregularly thickened and nodulose, 5-10 mm. in diameter. Apertures circular or oval, about 6 in 2 mm., separated by a series of mesopores. Acanthopores small, rather numerous. Diaphragms in the zooecia widely spaced.

From the associated B. implicatum it is distinguished by the greater development of mesopores, consequently more rounded apertures, thinner walls, and smaller acanthopores. The latter forms flattened branches.

Distinguished from B. jamesi (Bassler 1906, p. 18) by the thin-walled, angular zooecia, few mesopores, fewer diaphragms, and lobate to subfrondescent growth.

Zoarium of smooth, cylindrical or subcompressed infrequently dividing branches with conspicuous maculae of larger zooecia. Zooecia thin-walled, polygonal, mesopores practically wanting. Acanthopores variable. Zooecia 6-7 in 2 mm.

Zoarium a simple or branching frond articulating with a basal expansion. Zooecial apertures in diagonally intersecting series, surrounded by sloping hexagonal areas.

Zoarium ramose, branches acutely elliptical in cross-section, 3-6 mm. in width, with tapering articulating base. Apertures circular or elliptical 9 in 2 mm. along the diagonal rows. Margin nonporiferous.

Distinguished from E. falciformis by the more slender and comparatively thicker zoarium being compressed cylindrical rather than acutely elliptical in cross-section. Length, 1½-3 cm., width, 2-3 mm. Thickness 1-2 mm.

Eden from Cincinnati and vicinity. Bassler (1906, p. 36) notes that within the Eden there are all transitions to the broader forms of the typical E. falciformis. Similar forms occur also in the Greendale member of the Cynthiana at Lexington.

A thin, sharp edged, falciform frond. Length seldom over 50 mm., width usually less than 5 mm., thickness about 1 mm. Diagonal rows make an angle of about 60 degrees with each other and 30 with the edge of the frond. Occasionally a frond branches.

Fairview formation of Cincinnati and vicinity, occasionally also in the upper Eden. The Greendale member of the Cynthiana in Central Kentucky contains what is probably the same species.

A more robust form. Width up to 4 cm., length, 13 or more cm., thickness not exceeding 2-3 mm. It is characterized by the conspicuous, usually slightly elevated maculae several mm. apart, composed of larger apertures. Its growth may be falciform but more commonly it expands symmetrically from an articulating base.

Fairmount from Cincinnati and vicinity, and Greendale member of the Cynthiana in Central Kentucky.

A thin undulating expansion attaining much greater width and irregularity than E. maculata. Maculae relatively inconspicuous.

Fairview of Cincinnati and vicinity. It is also common in the basal Cynthiana of southwestern Fayette and adjoining parts of Jessamine County.

An unbranched, flattened frond, gradually expanding from an articulating base commonly 1-2 cm. in width and up to 10 cm. in length. It is characterized by the development of more or less discontinuous transverse ridges (monticules) which do not interrupt the diagonal series of apertures.

Characteristic of the Fairmount of the southern Bluegrass. A closely related form occurs in the Cynthiana.

Zoarium dendroid, of narrow, compressed, parallel edged branches continuous with an expanded base. Apertures in longitudinal rows.

Narrow branches 1.5-2 mm. wide, dividing at intervals of 4-7 mm. Zooecia in 9 (8-11) longitudinal rows, oblique with elliptical apertures, 16-18 in 2 mm. Six rows occur in the same distance. Interspaces comparatively thick, with a series of small grannules. Apertures of marginal rows directed outward in some specimens.

Common in the Lexington limestone, particularly the Jessamine, also rather common in the Cynthiana.

Associated with Escharopora ramosa in the upper beds of the Camp Nelson is a Rhinidictya, in growth essentially as in R. neglecta, but with conspicuous superior hemiseptum. There are 10-13 ranges of zooecia, 5-6 rows in 2 mm., and longitudinally 17 apertures in 2 mm. The marginal rows show the apertures directed slightly outward. Compared with R. fidelis the branches bifurcate more frequently, are a little wider with one or two more rows of apertures, and the zooecial tubes make a more acute angle with the median lamina.

Shell equivalve, smooth or with concentric growth lines. Hinge arcuate, with series of curved, transverse teeth. Cardinal area not striated. Ligament small, immediately behind the beaks. Adductor impressions subequal. This genus is abundantly represented in the local Ordovician.

Left valve convex, right flat, inequilateral, auriculate anteriorly and posteriorly. Area amphidetic, grooved longitudinally. Anterior teeth obscure, transverse, posterior elongate, nearly parallel to the cardinal margin. Posterior adductor scar large, anterior small, strong, located below the anterior wing.

Distinguished by the strong concentric growth lines and large anterior ear (Grabau and Shiner 1909, p. 419). Measurements of a typical specimen—hinge line 42 mm., beak to center of base along oblique umbonal ridge 37 mm., beak about one-third distance from the anterior end.

Equivalve, inequilateral, more or less winged posteriorly with beaks nearly or quite terminal. Valves ventricose, with byssal opening in the upper half of the anterior side, and marked by moderately strong radiating ribs. Two or three slender lateral teeth and several cardinals are present. Ligament external. Area striated.

Shell obliquely ovate, extending into acute curving beaks. Surface with about 45 radiating plications. Length of average specimen about 40 mm., greatest width about 3/4 length, convexity about 1/6 length. Anterior slope nearly straight making an angle of a little less than 90 degrees with the cardinal margin. Posterior angle quite obtuse rounding more or less gradually into the cardinal outline. Cardinal margin about one-half the greatest length of shell.

Distinguished from Byssonychia in the absence of cardinal and lateral teeth. It is more erect, than other Ambonychia-like forms, (Grabau and Shimer 1909, p. 432) and with no posterior alation.

This species is characterized by the long hinge line and the very oblique anterior and posterior margins, producing an elongate rather than erect form. The shell is strongly convex, the anterior slope of the more gibbous specimens practically vertical except for the protrusion of the bysal opening. Shell thick, radiating plications very flat and separated by very narrow and shallow grooves, readily overlooked. Measurements given by Foerste are: length 11 cm. from beak along the umbonal ridge, hinge area 6//2 cm. in length extending 5-8 mm. anterior to the beak. Hinge area 4-6 mm. high.

Very common in and characteristic of the Cynthiana, particularly the Millersburg phase.

Distinguished from Byssonychia in the absence of cardinal and lateral teeth. Distinguished from Allonychia in the more oblique form and strong posterior alation.

An unusually large pelecypod 8-10 cm. in length and almost as wide, alate posteriorly and marked by 30-40 strong radiating ribs. Anterior edge about at right angles to hinge line. Beaks sharp, slightly incurved, and situated at the anterior end of the cardinal margin. Byssal opening immediately below the beak, 6-7 mm. in diameter. In a specimen 8 cm. long the hinge has a length of about 5 cm. From 4-14 cartilage grooves extend from the end of the wing to the byssal opening.

A characteristic Richmond species known from the Arnheim to the Whitewater. In the region around Louisville it seems to be restricted to the Arnheim.

Shell thin, obliquely elongate very inequilateral, with small anterior and large posterior end. Beaks not prominent, near anterior end. Valves crossed by oblique depression extending backward from anterior portion of umbo, and marked by concentric lines of growth. Teeth absent. Anterior adductor scar large and deep, posterior one large but faint. Ligament chiefly external.

The principal features are the comparatively straight hinge line posterior to the beak, a moderately convex or nearly straight basal margin, absence of median sulcus, and conspicuous extension of the anterior margin of the shell in front of the beaks. The umbonal ridge disappears ventrally in the general convexity of the shell. Measurements after figures by Foerste (1914b, p. 282) are: length about 60 mm., height at beak about 1/3 length, height posteriorly about ½ length, beaks 10-11 mm. behind anterior margin; convexity of valve about 4 mm., angle between cardinal and ventral margin 11-12 degrees.

About 2/3 the size of M. modiolaris with concentric lines which become obsolete on the umbonal ridge. The basal margin is a little concave and the anterior end extends but little beyond the beaks.

Modioliform shells distinguished from Modiolopis by the presence of 2-3 cardinal teeth in each valve.

Volutions 2 or 3, gradually enlarging, scarcely contiguous. Carinated on the back, often on the sides, giving subquadrate cross section. Aperture with or without median notch in outer lip, no slit band. Shell without callosities. Surface reticulated or cancellated.

Average shell 20-25 mm. in diameter, of 2 or 3 strongly carinated volutions, rhombic-subquadrate in cross-section, and rapidly expanding. Side subangular or narrowly rounded, the dorsal slope gently convex with strong transverse furrows and subangular ridges, the umbilical slope almost flat, without undulations. Ventral side with sharp impressed zone. Umbilicus wide and deep. Surface marked by raised transverse lines with short connecting lines in alternating series. In the outer part of the last whorl there are commonly 7-8 of the transverse, and 8-9 of the short lines in 2 mm. There is no perceptible recurving of the transverse lines in crossing the dorsal carina.

Maysville and Richmond. A small variety, C. ornatus minor with a diameter not in excess of 11 mm. occurs in the Trenton of Minnesota and elsewhere.

This genus includes those forms which have commonly gone under the name of Protowarthia, a synonym. It is distinguished from Bellerophon in the absence of the slit band, in the lack of abruptly expanded aperture, and presence of revolving striae as well as growth lines.

The most common of the Ordovician Bellerophontids characterized by the evenly rounded dorsum, rounded apertural lobes, and moderately deep sinus which is U- rather than V-shaped. Surface marked by fine lines of growth crossed by fine revolving striae. The surface features are seldom preserved. Diameter up to about 25 mm., height about 4/5 diameter.

A Bellerophontid characterized by the lenticular form, compressed, sharply keeled volutions which expand gradually to the aperture. Outer lip with F-shaped excission continuing as a long and verv narrow slit. Inner lip without callosity. Surface with growth lines only, in which feature it is not typical of the Bucaniidae.

Shell from 15-30 mm. in diameter. Thickness about ½ diameter. Volutions 3½-4½, each embracing 1/3-1/2 of the preceding. Umbilicus 1/3 or less the diameter of the shell, with abrupt, subangular edge exposing all volutions. Aperture obcordate, indented below by the sharp dorsum of the preceding whorl. Surface concave bordering the sharp periphery and marked by fine rather indistinct lines of growth.

Shell subglobose. Umbilicus never large. Aperture generally expanded, with callosity on inner lip. Outer lip with central notch and with well developed slit band or elevated blunt keel. Surface with growth striae only.

Shell rarely exceeding 17 mm. in diameter, aperture flaring laterally, diameter somewhat in excess of height. Adult forms with rounded carina, surface flat or slightly excavated, in younger forms, with distinct slit band. Notch deep, rather narrow subrectangular. Fine growth lines approach the slit band nearly at right angles and are then abruptly deflected backward.

Spire more or less elevated. Whorls closely coiled, angular on the periphery, generally with several carinae, the peripheral one strongest. Umbilicus small. Outer lip more or less deeply notched, but no slit. Surface markings of growth lines.

Height 45-50 mm., volutions 8-10, moderately angular with thick subcentral peripheral band. Upper slope more or less concave in the lower half, upper half convex, sometimes obscurely carinate. Lower carina obscure, space above a little concave. Apical angle 25-35 degrees. Umbilicus minute covered by reflected inner lip in the narrow specimens. Surface with unequal growth lines, strongly recurved toward the peripheral band indicating a deep F-shaped notch.

Height 12-22 mm., apical angle 60-65 degrees with 6-7 volutions. Upper slope nearly flat. Lower carina never strong, the slope between it and the strong peripheral carina more or less concave. Band rounded, with growth lines strongly recurved toward it. Umbilicus small.

Distinguished from L. medialis by the smaller apical angle (usually about 52 degrees), lower carina more distinct, and the last volution tending to become free. Peripheral band prominent, sharp, trilineate. Surface markings of stronger growth lines with finer in between.

Shell sublenticular, subconical, sharply rounded at the periphery, almost smooth. Suture close, scarcely distinguishable. Umbilicus often filled by reflected inner lip. Aperture deeply notched, band obscure. Surface markings of growth lines and spirals.

Small, diameter 11-12 mm., height about ½ diameter, of usually four volutions, with shallow suture, the upper surface forming an almost even slope. Umbilicus filled by reflection of inner lip. Surface markings of fine growth lines and exceedingly fin spirals. The former are strongly deflected backward along the slit band which is located on the upper edge of the periphery. Inner lip essentially vertical in the Trenton forms, always more so than in the later forms.

Diameter about 25 mm., height about ½ diameter. Characteristic features are the open umbilicus with angular margin and flattened sides, and the unusually prominent and sharply curved outline of the lower lip. Upper side of last whorl a little concave because of the slight elevation of the peripheral band.

A small species about 12 mm. in diameter and 7 mm. high, of 4-5 volutions, distinguished by the thick ridge above, adjoining the suture, the elevated band on the upper edge of the periphery, and concave surface between. Umbilicus open. Base uniformly rounded.

Diameter 30-40 mm. distinguished from L. vitruvia by the broader curvature of the lower lip which is like that of L. progne, L. micula, etc., and the broader and less abrupt umbilicus without the angulation as in that species. With specimens commonly preserved in the Lexington limestone as molds, these criteria are difficult to apply. According to Ulrich, L. vitruvia has commonly been identified as this species.

Specimens of this type are very common in the Jessamine but seldom preserving the diagnostic features.

Distinguished from L. micula only in size, with diameter 25-35 mm. and from L. americana in the closing of the umbilicus which is more or less filled with shell material. In internal molds where the umbilicus is occupied by the same material filling the whorls the umbilicus was open. For this reason L. americana and L. vitruvia seldom have the umbilical cavity entirely free of the matrix material.

Shell sinistral discoidal, upper surface flat showing all of the few, rapidly enlarging whorls. Base convex, and strongly umbilicated. Surface marked by growth lines, revolving lines sometimes shown in the peripheral region. Ulrich and Schofield (1897, p. 1038) regard the shell as dextral with the flat surface the base.

Shell 50-60 mm in diameter, height, ½ diameter. Umbilicus deep, rather abrupt, from one-third to one-half the diameter of the shell in width, exposing half or more of the inner whorls. Operculum with nucleus at the inner angle.

Shell turbinate, non-umbilicated, with short spire, composed of few more or less ventricose whorls. Aperture oblique with reflected inner lip, always excavated. Surface with spiral lines and small ridges crossed obliquely by sharp lines of growth.

Distinguished from the C. bilix type by the more ventricose whorls and stronger surface markings. The curvature is uniformly convex with no sign of a shoulder at the suture. The revolving ridges are strong and between each pair there are usually several finer ones. Nine or ten of the principal carinae occur on the body whorl, five or six exposed on the higher whorls. Volutions never exceeding five. Suture deep.

Characteristic of the Cynthiana, particularly the Greendale and Millersburg phases. A small variety occurs in the Rogers Gap.

Distinguished from C. varicosum by the less convex whorls, shallower suture, and more slender spire with six to seven whorls. The surface markings are weaker and the columnar lip not as straight. Revolving lines either subequal or stronger ones with several weaker ones in between.

A turbinate shell, with height equal to or a little greater than width. Apical angle 55-75 degrees. Whorls 2 to 4, depressed convex, flattened or even a little concave centrally on the exposed outer part, with a shoulder-like convexity at both top and bottom giving a deeply impressed suture. Base of last whorl more or less flattened, narrowly rounded at the periphery. Surface with subequal revolving striae on the upper whorls, generally alternating on the body whorl, crossed diagonally by finer growth lines. These are exceptionally fine for the genus, about 12 in 2 mm. on the last whorl, 9-12 ridges occur on the exposed part of the upper whorls. On the body whorl about, 4 in 2 mm.

A variety distinguished by the much finer surface markings and almost constant concavity of the outer part of each whorl. The lower whorl commonly shows a series of transverse undulations but this feature is not constant nor restricted to it.

Rather characteristic of the Arnheim in the western area of outcrop in Kentucky, from the Arnheim and Waynesville in Ohio and Indiana, possibly also the Whitewater.

Minute spiral shells of rounded whorls loosely embracing so as to leave a deep suture and umbilicus. Surface smooth. Aperture circular, lip thin.

"Subglobose, wider than high, with much depressed spire of three rapidly increasing volutions; suture almost channeled; umbilicus small. Possibly pelagic protoconchs of other gastropods." (Grabau and Shimer, 1909, p. 673.)

Very common throughout the Trenton-Richmond. In Central Kentucky it is particularly common in the Woodburn where its occurrence is genetically related to the phosphate deposits.

Shell fusiform, whorls convex or flat. Aperture elongate oval, acuminate above, canaliculate below. Columella nearly vertical, slightly twisted, thin. Surface smooth or with revolving or longitudinal rows of small punctures.

Shell thick, of about 6 gradually expanding very depressed convex whorls the last forming about 2/5 the entire height of the shell. Apical angle about 32 degrees. Suture faint externally, deep in molds. Aperture elongate, obliquely subelliptical, somewhat acuminate at both ends. Surface smooth except for revolving rows of very fine punctae. Surface of molds with several more or less obscure revolving furrows. Height of average specimen 6-7 cm.

Specimens referred to this species are rather common in the Rogers Gap, the types coming from the type locality at Rogers Gap, Grant County.

Othocones with large, more or less eccentric siphuncle, the funnels extending only to the next preceding septum.

E. proteiforme is characterized by its enormous size, sometimes attaining a length of 10-15 feet, circular section, comparatively shallow chambers, and large submarginal siphon. The spacing of the septa increases toward the body chamber. Relative diameters of the shell and siphuncle in available specimens about 2:1.

Orthoceracones and cyrtoceracones, depressed elliptical in section, characterized by the large, nummuloidal siphuncle, short compressed funnels, and nearly globular sheaths. Septa often double.

A large species with deeply concave septa. Siphuncle excentric, large, the siphonal beads occupying fully two thirds the diameter of the shell. Endosiphonal walls thick.

Long slender, usually tapering orthoceracones with small central or subcentral siphuncle. Shell smooth or with transverse striae.

A rather rapidly expanding shell, circular in section, typically about 20 cm. in length, expanding from 5 to 35 mm. Septa moderately concave, closely spaced, less so toward the living chamber where 10 chambers in the above specimen occur in 40 mm. Siphuncle eccentric somewhat nearer center than margin, very small where passing through the septa, expanding to about 4 times that diameter within each chamber. Surface smooth except for the raised edges of the septa which form narrow rings and the presence opposite the siphuncle of a narrow raised longitudinal line extending the length of the shell, slightly interrupted just above each of the annular rings.

An important horizon marker at the top of the Fort Ancient member of the Waynesville, known as the O. "fosteri" horizon. It is listed by Cumings from the McMillan and lower Arnheim of Indiana.

Cephalon very broad proportionately with long genal spines, and broad, regularly pitted border. Glabella inflated, pear-shaped, smooth or with indistinct furrows. Eyes generally absent. Thorax of 6 segments which are nearly straight at their extremities; axis narrow. Pygidium with margin entire. (Grabau and Shimer 1909, p. 258))

Head semicircular or subcrescentic, typically about, 10 mm. long, 15 mm. wide, convexity of about 6 mm. Genal angles with or without spines. Glabella smooth, very prominent, produced posteriorly into a short, blunt spine. Anterior and lateral margins surrounded by a broad flattened border, marked by 3-5 concentric rows of deep rounded pits in front and one or two additional rows laterally, becoming irregular toward the genal angles. More familiarly known as "Trinucleus concentricus."

Particularly common in the Eden,, also in the Cynthiana. It is listed by Nickles from the Point Pleasant beds (1902, p. 64). It occurs in large numbers thirty feet above the Cornishville and about 75 feet below the Plectambonites layers of the Million in Lincoln and Boyle counties.

Elliptical. Cephalon semicircular. Glabella large and well defined with straight sides and rounded front, marked by three deep furrows extending toward the center from each side. Eyes small. Central axis of thorax wider than lateral lobes; furrows of axis not continuous with those of pleura. Thoracic segments 14-16. Pleural segments grooved. Pygidium with 6 segments in the axis and with entire margin. (Grabau and Shimer, 1910, p. 286)

Length about 20 mm., width, 0.5 length. Center of each axial segment marked by a tubercule.

Isotelus belongs to the subfamily Asaphinae with bifurcated hypostome. Carapace oval with broad axial lobe, and obsolete segmentation of pygidium and glabella. Eyes large and prominent. Thorax of eight segments, pleura grooved, with rounded extremities. Free cheeks large, the suture emerging well within the genal angles.

A large species commonly attaining a length of 200-250 mm., at times practically double the figure. Width somewhat over half the length. Axis forming about one-half the width. The most distinctive feature is the subtriangular form of the pygidium with length about 3/4 width. Cephalon similarly subtriangular. Genal spines short, present only on the smaller specimens.

This species has commonly been distinguished from the preceding by the development of genal spines extending back as far as the fifth or sixth thoracic segment. According to Raymond and Narraway (1910, p. 55) the pygidium is short and rounded, contrasting with the subtriangular form of I. gigas. In this it agrees with the young individuals of that species. It does not attain the large size of I. gigas.

Shell large, suboblong with oblique backward swing. Ventral outline rounded, greatest thickness ventrally, lower edge usually blunt. Right valve overlapping the left ventrally. Hinge simple. Surface frequently horny, smooth and glossy, in some specimens grannulose or punctate. Eye spot usually present on antero-dorsal fourth. Large, rounded, subcentral muscle scar well marked on the interior, sometimes discernible externally.

Shell obliquely subovate, length about 3 mm., width 2/3, and thickness 1/3 length. Anterior end but little produced beyond hinge, posterior end protruding about one-third the length of the shell. Anterobasal margin sloping abruptly. Otherwise much like L. fabulites. Eye tubercule obsolete.

A variety distinguished in that it "has the dorsal angles sharper, an appreciably flattened border or flange at the ends of both valves and the ventral edge is a trifle more convex. The eye tubercule, and the reticulated spot as well, is, though always very small, generally distinguishable." (E. O. Ulrich, 1890, p. 177.)

Shell obliquely subovate, length 10-11 mm., height, and length of hinge about 2/3 length, thickness about 4 mm. Height of ends about as three is to four, both obliquely and about equally truncate above, the anterior end narrowly and posterior end more broadly curved. Ventral edge gently rounded, overlap strongest ventrally. Eye tubercule faint.

An average large specimen shows the following measurements: Length 20 mm., width 13 mm. Length of hinge 14mm. In available specimens the length varies from 8-25 mm. Posterior end more produced than anterior, hinge extremities slightly mucronate. Eye spot sharp, near dorsal margin.

Developed in great numbers in the Salvisa, particularly where the rock is more granular and somewhat argillaceous, associated with several species of Leperditia.

Shell oblong or subovate, posterior two-fifths bulbous or sub-globular, bordered anteriorly by a deep, obliquely curved sulcus which extends from the dorsal margin more than half way across the valves postero-ventrally. Anteriorly another oblique, but shallower sulcus. Dorsal margin long and straight, hingement simple. Ventral edge thick, contact margin generally with a row of small spines on each side, and concealed on lateral view by an extended, flattened border.

Shell subovate, length 1½-2 mm., width 2/3 length, length of hinge 3/4. Anterior and posterior widths subequal, curvature of the two ends much alike, the posterior end curves in farther dorsally making a more acute angle with the hingeline. Posterior sulcus crescent shaped, narrow and deep. Anterior sulcus not so well defined. No eye tubercule. Surface minutely granulose.

¹Thruout the paper the mature and immature regions are indicated by (m) and (im).
²Cumings (E. R. 1902, pp. 197-217) has questioned the distinctness of the three genera Heterotrypa, Dekayella and Dekayia.

ORDOVICIAN FAUNA