Logan.] The Invertebrates , Fort Pierre Group. 505 



lee ted by "West and labeled Inoceramus cuneatus, following Meek 

 and Hayden's classification. (See reference above.) The 

 specimens collected by West were from the Fort Pierre shales 

 near Wallace, on the Nork Fork of the Smoky Hill river. 



Inoceramus inciirvus M. & H. 



Inoceramus ineurvus M. & H., 1876, U. S. Geol. Surv. Terr., vol. ix, p. 61, 

 pi. xii, ff. 4a, b. 



Meek's description : " Shell snbglobose, oval or ovate cardi- 

 form, very gibbous, nearly or quite equi valve ; beaks oblique, 

 placed a little back of the anterior side, strongly incurved ; urn- 

 bonal elevated above the hinge and points of the beaks and very 

 ventricose in both valves. Surface ornamented by concentric 

 undulations, which become sharply elevated over the most 

 prominent portions of the umbones, but are less distinct or 

 nearly obsolete toward the base and extremities of the shell. 



"Judging from the curve of the undulations near the beaks, 

 young individuals of this species must have been nearly ovate 

 in form, the posterior side being broader than the other. At 

 this stage of its growth, the shell seems to have been much less 

 convex, and the beaks more nearly terminal ; but as it advanced 

 in age it became rapidly more ventricose and extended some- 

 what in front of the beaks. The surface was probably marked 

 by lines of growth, but, owing to the exfoliation of the external 

 fibrous layer, they are not preserved on our specimens, none of 

 which are in a condition to give a very clear idea of its gen- 

 eral form. The peculiar and equally incurved character of the 

 beaks, together with the ventricose, elevated umbonal region 

 and sharply prominent undulations, when taken together, will 

 serve to distinguish it from any other species known from these 

 rocks." 



A rather incomplete cast of what is evidently a young indi- 

 vidual occurring associated with /. cripsii, I somewhat doubt- 

 fully refer to this species. The specimen was collected from 

 Fort Pierre shales, a few miles northwest of Atwood, in Raw- 

 lins county. Fragments of nodules containing similar casts 

 were found in the shale thrown from a well a few miles west of 

 this locality. 



