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strong and regular, especially over the upper or umbonal portion; sometimes fainter and more irregular.

In its general plan this species may be compared with Posidonomya fragosa from the White Pine shale of Nevada, but the figured specimens show numerous differences from that species. C. percostata has a longer hinge line and a broader shape. The ribs are fewer, coarser, stronger, and more angular. Although this is true of the specimens selected for illustration, the shells vary so greatly in themselves and in many cases are so imperfect that these differences are at times much less marked.

C. percostata is also related in a general way to C. richardsoni. The shape does not greatly differ; the chief distinction rests in the plications, those of the present species being much coarser and less numerous. Nevertheless, both forms vary freely. As elsewhere remarked C. richardsoni manifests a distinct tendency to obsolescence of the lateral ribs. A specimen of that species with the ribs more than usually coarse and restricted to the mesial portion would approach very closely to a specimen of the present species in which the plications were more than usually fine. Both cases are found in the specimens examined; and as, owing to their imperfect condition, it is impossible to take all characters into account, it happens that in given instances one can not refer an aberrant example with any confidence to one species rather than another. For my own part I have been somewhat guided by the character of the dominant form when, as proved usually to be the case, only one species was present in its typical expression.

Horizon and locality.—Caney shale, McAlester quadrangle (station 2078), Atoka quadrangle (station 2082?), Tishomingo quadrangle (station 2084).

CANEYELLA RICHARDSONI n. sp.

Plate IV, figures 1, 1a.

Shell of medium size, strongly oblique and transverse. Umbones prominent. Hinge line long, somewhat shorter than the width. Posterior outline nearly straight above, meeting the hinge at an obtuse angle, becoming more and more strongly bowed below until it assumes an upward direction, when it again becomes nearly straight; slightly sinuous toward the hinge in connection with the byssal sinus.

Surface marked by numerous rather fine ribs, which divide, and thus tend to form groups of two or three. Ribs more or less finer and fainter toward the sides and tending to become obsolete all over, so that occasionally a small specimen shows only a few obscure ones over the mesial portion; frequently quite flexuous. There are also numerous concentric striæ of varying strength, less marked than the costa, with which they produce a somewhat cancellated effect.

In being provided with costæ this species shows its relationship to C. percostata, but is distinguished by the fact that the ribs are finer and more numerous. C. richardsoni belongs also to the group of which the form described by Meek as Posidonomya fragosa is an example, and some specimens in which the costæ are nearly obsolete, except for a few down the middle, suggest the western form quite strongly. The typical variety, however, can hardly be confused, and even shells with obsolete costæ differ in shape rather widely from Posidonomya fragosa.

Horizon and locality.—Caney shale, McAlester quadrangle (station 2078), Stonewall quadrangle (station 2081), Tishomingo quadrangle (station 2083).

Genus PARALLELODON Meek.

PARALLELODON MULTILIRATUS n. sp.

Plate III, figures 4, 4a, 5.

Shell of medium size, transverse. Posterior extremity truncate in the usual manner. Inferior outline rather strongly convex, curving upward somewhat suddenly in front and apparently somewhat retracted as it meets the hinge line. Beak moderately prominent and situated a short distance back from the anterior margin. Umbonal ridge well up toward the hinge line.

Surface marked by very fine radiating liræ, which are coarsest near the cardinal line on the posterior side and gradually become finer and fainter toward the front until most of the umbonal region and all the anterior half of the shell appear to be smooth. There are in addition very fine, faint, concentric lira.

In the fineness of its radii this species seems to stand alone among the American representatives of the genus, and I find it hardly necessary to point out other differences between the present species and such others as are sufficiently known to allow of careful comparison. Some undescribed forms from the Chester have equally fine radii and may prove to be the same, though they are more highly convex.

Horizon and locality.-Caney shale, Atoka quadrangle (station 2089), Tishomingo quadrangle (station 2085).

Genus CONOCARDIUM Bronn.

CONOCARDIUM sp.

Aside from the peculiar shells for which the genus Caneyella has been established, but few species of pelecy pods are accounted for in this report. A number of types are in fact contained in our collection, but they are too imperfectly known even to appear in the body of this account of the Caney fauna as indeterminata. Although represented by but two individuals, and rather fragmentary ones, the

present form is of sufficient interest, and can be described in sufficient detail, to merit separate recognition.

The shape was triangular, the truncated tubular anterior portion being missing. The anterior and cardinal margins are nearly straight and of nearly equal length, about 13 mm. in one specimen. The inferior-posterior margin is gently convex, and in the same specimen about 20 mm. long. The inferior-anterior and the superior-posterior angles, therefore, are acute, and the anterior-superior angle is obtuse. The surface is marked by a considerable number of fine, sharp liræ, separated by rounded striæ considerably wider than the lire. Frequently smaller lira arise by intercalation between the larger ones. There are about twelve of the large liræ in a distance of 5 mm., and from two or three to eight or nine small ones additional. The latter, however, may have attained such a size that they are not conspicuously alternating.

Horizon and locality.-Caney shale, Atoka quadrangle (station 2077).

PTEROPODA.

Genus IDIOTHECA n. gen.

Shell rather small, short-conical, oblique, laterally compressed. Anterior end (if that nearest to the apex may be provisionally thus designated) narrower than the posterior, and marked by a sinus or groove. Posterior end strongly rounded. Sculpture consisting of transverse wrinkles, which are strongest across the anterior end and almost obsolete across the posterior, where also they are deflected downward. Shell substance phosphatic or chitinous (?).

I am quite at a loss regarding the affinities of this interesting form. After canvassing several different groups it seems to me probable that it belongs to the Conulariidæ, the shell substance, so far as preserved, suggesting Conularia itself. It may possibly be an aptychus of one of the Goniatites, which occur so abundantly at a little higher horizon, or it may be a gasteropod related to the much older genus Stenotheca. That it is a laterally compressed discinoid I regard as a hardly possible hypothesis.

IDIOTHECA RUGOSA n. sp.

Plate V, figures 6, 6a, 6b, 6c.

Shell rather small, rapidly expanding, obliquely conical, strongly compressed. Height about three-fourths of the greatest length. Apex about three times as far from one edge as from the other. For convenience the end nearest the apex may be called the anterior, although it is at present not possible to homologize the parts with any known shell. The width of the aperture is much less than the length, but it is difficult to express the ratio numerically, since the shape is irreg

ular, the anterior end being narrower than the posterior. There is besides an impressed zone or sinus traversing each side from the apex to the aperture a little posterior to the middle. The posterior end is broadly rounded. The narrower anterior end appears to be concave, the concave portions joining the sides in acutely angular edges.

The surface is marked by fine transverse corrugations, which are strong over the anterior half of the shell and increasingly faint toward the posterior, where they are almost or quite obsolete. Their direction is not strictly transverse, as they bend rather strongly downward just before dying out near the posterior portion. This area, which, as already remarked, shows almost no trace of transverse wrinkles, is obscurely marked by very fine longitudinal striæ.

The anterior edge of the specimen is unfortunately not very perfect. The structure appears to be as described above, but this configuration may be due to accidental causes and to lateral compression, which upon this hypothesis would have more or less greatly diminished the width in proportion to the length and have crushed and dislocated the anterior end. While, therefore, it is possible that the section may have been more nearly circular and the anterior end rounded instead of reentrant, I am inclined to doubt this, the shape at present being quite symmetrical and showing no signs of compression over the posterior end, which must have been affected only less strongly than the front.

The only specimen found is covered in part with a dark chitinous (?) or carbonaceous (?) layer, the remainder being white and polished, as if phosphatic. While there may have been whitish phosphatic matter forming a part of the shell, the appearance noted is probably due to the specimen's being almost an internal mold in a very siliceous rock, essentially a chert.

Horizon and locality.-Woodford chert (?), Atoka quadrangle (station 5114).

SCAPHOPODA.

Genus LÆVIDENTALIUM Cossmann.

LEVIDENTALIUM VENUSTUM Meek and Worthen.

1861. Dentalium venustum. p. 145.

Plate V, figures 5, 5a.

Meek and Worthen, Acad. Nat. Sci. Phila., Proc.,

St. Louis limestone: Waterloo, Monroe County, Ill.

1866. Dentalium venustum. Meek and Worthen, Geol. Surv. Illinois, Rept., vol. 2, p. 284, pl. 19, fig. 8.

St. Louis group: Waterloo, Monroe County, Ill.

1903. Plagioglypta venusta. Girty, U. S. Geol. Survey, Prof. Paper, No. 16, p. 453. The species subsumed under this title comprises straight, slender, very gradually expanding, subcylindrical shells having a circular sec

tion. The surface is without sculpture, the best preserved showing only almost imperceptible growth lines. A characteristic specimen has a length of 14 mm., with a diameter at the larger end of a little more than 14 mm., and at the smaller of 1 mm. Other specimens are about the same.

I am uncertain as to the real affinities of this form, but the probabilities seem to be much more favorable to placing it with the Dentaliidæ than with any other group. I have considered the genera Styliola and Coleolus, but rejected them because of the much more rapid taper which is found in the most typical species of those groups. While some of the individuals at first provisionally included here proved upon closer inspection to be septate, and so to belong to Orthoceras or Bactrites, it seems almost certain that others are not so. The figured specimen shows traces of neither septa nor siphuncle, and it is almost too long to be the chamber of habitation of a small orthoceratite. Some of the other shorter fragments may really be of this nature; I know of no way of determining. These forms are almost too large and too straight to be the spines of some other organism, such as Productus, and that possibility has been dismissed.

The same or a closely related species occurs in the Spergen limestone fauna, where it has been described as Dentalium venustum. Most of our specimens from that fauna are larger, and some are more rapidly tapering. One in size and shape is almost a duplicate of that from the Caney shale selected for illustration. The latter in many respects is similar to L. illinoisense, but is much smaller and less rapidly expanding.

In discussing our Carboniferous Dentaliidæ in 1903 I referred this species and D. illinoisense to the genus Plagioglypta. Plagioglypta is distinguished by being marked with obliquely transverse striæ, while these two species are almost absolutely smooth. It seems rather better, therefore, to place them under Lævidentalium, although Lævidentalium consists typically of curved shells, while these are straight.

Horizon and locality.-Caney shale, Antlers quadrangle (station 3948), Tishomingo quadrangle (stations 2083, 2091).

GASTEROPODA.

Genus PLEUROTOMARIA Defrance.

PLEUROTOMARIA? sp.

Plate V, figure 4.

Our collection includes but a single specimen of this form, one so imperfect, withal, that only a partial description can be given of it.

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