Logan.] The Invertebrates, Niobrara Group. 493 



ginning and ending at a distance from the margins of the shell ; 

 a singular twisted callus composes the hinge, the back of which 

 is transversely ribbed. 



"Length greater than height; hinge line very long ; ridges 

 concentric, about twelve in number, extending into the cavity 

 under the hinge, submargin thick ; test composed of columnar 

 transverse fibers. No muscular impression can be traced unless 

 the ridges indicate their station. The posterior side of the shell 

 is slightly elongated. The exterior of the shell, and in many 

 specimens the interior, covered with Ostrea congesta." 



Stanton 09 has made H. grandis, H. capax and H. eccentricca 

 synonymous with Inoceramus deformis. The test of I. deformis 

 is much thinner than that of H. grandis ; the shell is more con- 

 vex ; the ridgss more acute ; the marginal border narrower ; the 

 side more triangular. So, after a careful examination of many 

 specimens, including both adult and young, I decided to return 

 to Conrad's classification. I am inclined to think, however, 

 that Haploscapha is better as a subgenus under Inoceramus. 

 Should such a classification as I have suggested be made, then 

 I. deformis would properly belong to that subgenus, as it corre- 

 sponds more nearly to the form of Haploscapha in general char- 

 acteristics. 



I. deformis occurs near the upper surface of the Fort Hays 

 limestone, but I have never found it in a higher horizon. The 

 different forms of Haploscapha occur in the lowermost Ornitho- 

 stoma beds, and are abundant in this horizon throughout the 

 Niobrara area. They are especially abundant a few miles south 

 of Castle Rock, in Trego county ; on the Saline river a few miles 

 north of Ellis, in Ellis county, and near Marvin, in Phillips 

 county. 



Haploscapha niobrarensis, n. sp. Plate cxvi, fig. 2. 



Description : Shell large, subtriangular, hinge line short ; test 

 thick in both young and adult specimens, convex — convexity 

 greater than in any of the other species. Ridges broadly 

 rounded, passing into a smooth margin gradually. Smaller 



69. Stanton, T. W., U. S. Geol. Surv. Bull. 106, 1893. 



