314 PALEONTOLOGY OF OHIO. 



in outline, and provided with a ridge or obtuse carina along its entire 

 length; aperture oval-suborbicular, being slightly longer than wide; lip 

 more or less sinuous at the middle of the anterior side, on one or both 

 sides of the termination of the central ridge of the anterior slope, which 

 ridge terminates in a little projection at the margin. Surface marked 

 by fine lines of growth, which are most distinct on the anterior slope, 

 where they curve backward as they approach the mesial ridge, and then 

 abruptly forward in crossing the ridge ; extremely faint traces of minute 

 radiating strise apparently also exist; apex rather abruptl}^ pointed and 

 directed backward without any lateral obliquity. 



Length, measuring obliquely from apex, 0.97 inch ; breadth, 0.82 inch ; 

 length from anterior to posterior margin, 0.90 inch; height of apex, 0.44 

 inch. 



This species is remarkable for its regular, depressed, obliquely conical 

 form and non-spiral apex, which is merely obtusely pointed and directed 

 backward without the slightest lateral curve. It therefore departs widely 

 in form from the typical species of Platyceras, and agrees more nearly 

 with an Oriskany shell described in the third volume of the Palaeon- 

 tology of New York, under the name Cyrtoliiesf expansus, excepting that 

 its apex is not so attenuated and produced. Although probably not a 

 true Platyceras it seems to me more nearly allied to the section of the 

 same, for which the name Orthonychia has been proposed, than to Cyrto- 

 lifes, which was founded on a very difierent type (C ornatus, Con.), with 

 a peculiar style of ornamentation. In its surface markings our shell 

 agrees with Platyceras, being merely marked with fine lines of growth, 

 more or less undulated on the anterior slope, while the traces of very fine 

 radiating striae indicate relations to the section Orthonychia, with which 

 the shell also agrees more nearly in its non-spiral form. It therefore 

 bears the same relations to the elongated forms of Orthonychia that those 

 depressed, rapidly expanding species of Platyceras, such as P. calanticum 

 and P. obesum, bear to the typical forms of the latter genus. 



Locality and position : Lodi, Ohio. Waverly group of Lower Carboniferous. 



Genus PLEUROTOMARIA, Defrance, 1826. 

 (Diet. Sci. Nat., XLI, 381.) 



Pleurotomaria textiligera, Meek. 



Plate 13, figs. 7a, b. 

 Pleurotomaria textiligera, Meek (1871, Proceed. Acad. Nat. Sci., Philad., XXIII, 176. 

 Shell attaining a medium or somewhat larger size, turbinate or rhom- 

 bic, suboval in general outline, with height a little greater than the 



