NATURAL SCIENCES OF PHILADELPHIA. 177 



Xjocality and position. Medina, Ohio. Waverley group of the 

 Carboniferous, where it seems to be quite abundant. 



PLETJROTOMARIA GTJRLEYI, Meek. 



Shell small, with breadth somewhat greater than its height ; 

 spire depressed-conical, slightl}^ obtuse at the immediate apex ; 

 volutions five and a half, convex, and near the apex rounded, but 

 becoming nearly rectangular farther down, the angle being at the 

 middle of those of the spire, and passing around above the middle 

 of the body whorl, which is rather convex but not much produced 

 below ; upper side of all the volutions (excepting the rounded ones 

 near the apex) sloping a little and flattened or slightly concave 

 from a linear revolving carina just below the suture, outward to the 

 mesial angle, below which the outer side is verticallj^ flattened and 

 smooth ; suture canaliculate ; revolving band very narrow, rather 

 distinctly concave, with a linear ridge or minute carina along each 

 margin passing around upon or just above the mesial angle; 

 umbilicus very small. Surface on the inner side of the body vo- 

 lution ornamented by about fourteen distinct raised revolving 

 lines, the upper of which are somewhat larger than the others, 

 and on the upper slope above the mesial angle, by three or four 

 very small revolving lines ; while the small rounded whorls near 

 the apex are each occupied by about six revolving lines ; striae of 

 groAvth yQvy minute, and, on the upper slope and flattened outer 

 side of the whorls, very strongly and abruptly curved backward to 

 the band, so as to indicate an unusuall}^ profound, rapidly widen- 

 ing sinus iu the lip. Aperture wider than high, and obliquely 

 subrhombic in form. 



Height, 0.17 inch ; breadth, 0.20 inch ; slopes of spire straight; 

 divergence of same nearly rectangular. 



This little shell has much the form and general appearance of 

 P. Graymllensis, N. & P., but ma}' be distinguished at a glance 

 by the differences in the details of its sculpturing ; and particu- 

 larl}' by the smooth vertically flattened outer side of its volutions, 

 on which the lines of growth are seen, by the aid of a magnifier, 

 to be much more obliquely curved backward than those on the 

 corresponding part of P. Grayinllensis. It must be very rare, as 

 I have seen only the single typical specimen among all of the Coal- 

 measure fossils of the western States and Territories that have 

 ever come under my observation. 

 1871.] 



