460 PROCEEDINGS OP THE ACADEMY OF 



Length - 24 inch ; breadth 0.18 inch ; apical angle convex, divergence 

 about 37. 



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

 Measures. Abundant. 



Pleurotomaria subsinuata. Shell, conical ovate ; spire elevated ; volutions 

 six, convex, last one, in mature shells, sometimes obliquely flattened a little 

 above, just below the suture, thence rounded below; suture linear, but occupying 

 a more or less deeply rounded depression ; spiral band not well defined, 

 angular, located above the middle of the body whorl, at the lower edge of the 

 slight flattening of its upper side, and passing around the middle of the upper 

 turns ; sinus of the lip, judging from the curve of the lines of growth in crossing 

 the band, shallow, and not very clearly defined ; aperture subcircular; columella 

 indented in the umbilical region, but not distinctly perforate. Surface 

 ornamented by about fourteen to eighteen distinct revolving lines, three of 

 which, on the middle of the last turn, are larger than those above, while those 

 below gradually diminish in size toward the umbilical pit ; only two or three 

 of the smaller lines usually occupy the slightly depressed upper part of the 

 whorls, where they are crossed by a series of regularly arranged, transverse 

 costae or wrinkles ; lines of growth obscure. 



Length 0-40 inch ; breadth 0-31 inch ; apical angle convex, divergence 55. 



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

 Measures. 



Pleurotomaria Chesterensis. Shell of medium size, turbinate ; spire 

 moderately elevated ; volutions about six, increasing rather gradually in size, 

 convex, distinctly carinated around the middle, and flattened, or a little concave 

 above and below the carina, the flattened space above being oblique, and that 

 below vertical ; last whorl provided with a second carina below the other, and 

 a little convex on the under side ; suture linear ; umbilicus small, or nearly 

 closed ; surface marked by numerous fine, regular, thread-like revolving lines, 

 crossed by similar striae, which, in traversing the spiral band, which occupies 

 the space on the middle of the body whorl between the two carinas, make a 

 gentle backward curve, parallel to the border of the rather shallow sinus of 

 the outer lip ; aperture subcircular, approaching a subquadrate outline. 



Length 0-75 inch ; breadth 0-72 inch ; apical angle regular, divergence about 

 60; breadth of spiral band 0-14 inch. 



Similar in form and general appearance to P. tabulata, Conrad, but differs 

 in having a small umbilicus, while the axis of that shell is not perforate. It 

 also differs in having a much broader spiral band, which occupies the space 

 between the two carinae, instead of coinciding with the upper angle. Again 

 the upper carina of the shell under consideration is never crenulated, as in 

 Conrad's species. 



Locality and position. Chester, Illinois. Chester Limestone of the Lower 

 Carboniferous series. 



Pleurotomaria subscalaris. Shell large, rather thick, conical ovate ; spire 

 moderately elevated ; volutions six, those near the summit of the spire flattened, 

 the others convex, and provided with a distinct, sharp carina, which occupies 

 a position a little above the middle of the body whorl, passes around near the 

 middle of the second, becomes lower on the third, and sinks below the suture 

 on the others. Below this angle there is on the body volution, a second less 

 distinct subangular prominence, with a broad, vertical, nearly flattened, or 

 slightly concave space between the two. Under side of last turn a little convex, 

 and the umbilical region somewhat indented, but not perforate ; suture well 

 defined. Spiral band narrow, and occupying the principal angle of the whorls. 



The surface of our specimen is somewhat eroded, but it retains traces of 

 about twenty rather strong revolving lines, eight or nine of which occupy the 

 upper side of the whorls, above the carina, some three or four the flattened 



[Oct. 



