NATURAL SCIENCES OF PHILADELPHIA. 461 



rater side of the body whorl, and the remainder the under side. On the upper 

 sloping surface of the whorls there are also regularly arranged, oblique 

 transverse stride, which, in well-preserved specimens, are probably continued 

 upon the outer and under sides of the last turn. 



Agrees with P. tabulata, Conrad, in size and general appearance, but differs 

 in having the upper whorls of the spire more depressed, and without any angle 

 visible above the suture. The principal angle on its lower whorls also appears 

 to be destitute of the crenulation, so distinct on that of P. tabulata. 



Length 1-67 inch; breadth 1-52 inch; apical angle convex, divergence 70. 



Locality and position. Macoupen County, Illinois. Lower Coal Measures. 



Pleurotomaria speciosa. Shell attaining a medium size ; spire moderately 

 elevated ; volutions seven to seven and a-half, sub angular just below the suture, 

 thence obliquely flattened to a much more distinct revolving angle a little below 

 the middle of the upper turns, and about the middle of the body whorl. Below 

 this second angle the outer side of the last turn is vertically flattened or a little 

 concave, so as to produce a third obtuse revolving prominence below the 

 middle, beneath which the under side of the whorl is convex. Suture well 

 defined. Spiral band narrow, very prominent, angular and regularly crenu- 

 lated by cross lines, occupying and partly forming the middle angle of the 

 body whorl, which passes around on the upper whorls a little more than 

 one-third of their breadth above the suture. Aperture subcircular, approaching 

 subpentagonal ; umbilicus small. Surface ornamented by eighteen to twenty- 

 two thread-like revolving lines, about twelve of which occupy the under side 

 of the body whorl, four to seven the upper slope, and two or three the outer 

 flattened space. Crossing all these there are numerous extremely fine, very 

 regular, closely arranged transverse lines, about every fourth or fifth one of 

 which is considerably enlarged near the suture ; and they all curve obliquely 

 backwards in approaching the spiral band. 



Length about 0-55 inch ; breadth 0-51 inch; apical angle regular, divergence 

 82; breadth of spiral band not more than about 0-03 inch. 



Locality and position. Hodges Creek, Macoupen County, Illinois. Coal 

 Measures. 



Pleurotomaria turbiniformis Shell rather large, trochiform, height and 

 breadth nearly equal; spire conical, moderately elevated; volutions about five 

 and a half to six, flat, last one distinctly angular around the outer side, and 

 flattened or slightly convex below; umbilical region somewhat excavated, but 

 not perforate; spiral band extremely narrow, grooved, occupying the angle 

 around the outer side of the body whorl, and passing around scarcely above 

 the suture on the other volutions, margined above and below by a sharply 

 elevated line; suture linear, but well defined, having a somewhat banded 

 appearance, in consequence of the development of a rather distinct revolving line 

 at the upper margin of each whorl; aperture apparently rhombic subquadrate. 

 Surface ornamented by about twenty obscure, closely arranged, revolving striae, 

 crossed by stronger, very regular transverse lines, which are most distinct on 

 the upper part of the whorls, and pass with a gentle curve obliquely 

 backwards and outwards to the spiral band. Below the angle the body 

 whorl is nearly smooth, or only marked by very obscure lines of growth, and 

 faint traces of revolving striae. 



Length about 0-93 inch; breadth nearly 0-97 inch; apical angle regular, 

 divergence 64. 



Locality and position. Lasalle, Illinois. Upper Coal Measures. 



Pleurotomaria scitula. Shell small, trochiform, length and breadth nearly 

 equal; spire depressed conical; volutions six, a little convex, last one prominent 

 and narrowly rounded or subangular on the periphery, slightly convex below; 

 suture somewhat channelled ; aperture subcircular, approaching a subquadrate 

 form; umbilical region impressed, but not distinctly perforate; spiral band 



I860.] 32 



