FOSSILS OF THE COAL MEASURES. 603 



so many specimens of it not exceeding the dimensions given above, 

 while no nearly allied large species is known in the same association, 

 wr would think it might be a young shell. It is perhaps more nearly 

 like onr P. mh-foncmn than any of its associates yet known, but in 

 addition to its vastly smaller size (although having nearly the same 

 number of whorls), it differs in being much more depressed, and having 

 proportionally much more slender whorls; while its spiral band pa- 

 around the middle of its body whorl, instead of between the middle and 

 the upper margin. In the position of its baud, it is nearer like P. Beck- 

 icithnna, of McChesney. but it differs so widely from that species in size 

 and other characters, as to render a close comparison unnecessary. 



Locality <tn<l position Lower part of the Coal Measures, on Hodge's 

 creek, Macoupiu county, Illinois. 



PLEUROTOMARIA CONOIDES, M. and W. 



PL 28, Fig. 1. 

 Plturotomaria eunoides, MSKK and WORTHKX, 1866. Proceed. Acad. Ifat Sci., Phila., p. 271. 



SHELL small, regularly conoid trochiform, longer than 

 wide, the breadth being to the length about as five to six. 

 Volutions five or six, increasing regularly and rather grad- 

 ually in si/e, all obliquely flattened nearly parallel to the 

 slope of the spire, though the lower margin of each projects 

 at the suture slightly beyond the upper edge of the succeed- 

 ing one below; last one angular around the periphery at 

 the base, and flattened on the under side at less than a right 

 angle to the oblique slope above, but rounding abruptly 

 into the minute umbilical perforation within. Aperture 

 rhombic quadrangular, with nearly equal length and 

 breadth; inner lip straight and parallel to the axis of the 

 shell below, but curving out abruptly at its base. Surface 

 ornamented with small, regular, oblique, arching striae on 

 the upper sloping sides of the whorls, and minute sigmoid 

 lines, crossed near the periphery by faint traces of a few 

 revolving stria' on the under side of the body whorl. 

 Spiral band narrow, located at or slightly above the per- 

 iphery of the body volution, and passing around its own 



