48 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



less depressed form, and much more tumid, less nearly terminal, and gener- 

 ally constricted beaks, will readily distinguish it from the Indian species. 

 The specimens yet found are mainly casts, retaining more or less of the outer 

 fibrous layer of the shell only. 



Locality and position. — Both these forms occur in a brown Cretaceous 

 sandstone at the mouth of Judith River, above Fort Union ; from the horizon 

 of the upper part of the Fox Hills group. 



I ii ©cc ram us Cripsii! var. suite o in press us, M & H. 



Inoceramus Cripsii, Mautell (1822), Foss. South Downs, or 111. Geol. Sussex, 133, pi. xxvii, fig. 11. — 

 ? Goldf. (1833), Petref. Germ. II, 1 16, pi. cxii, tigs. 4, a, b.— Zittel (1864), Bivalves of tbe 

 Gosau formation, tab. xiv, figs. 1 and 2 (varieties and synon.?) 



Inoceramus subdepressus, Meek and Haydeu (1860), Proceed. Acad. Nat. Sci. Philad., XII, 181. 



Shell transversely rhombic-oval, compressed, thin, anterior side rounded 

 below the beaks ; base forming a long semi-ovate curve, the most prominent 

 part of which is behind the middle ; posterior side long, very narrowly 

 rounded, and prominent below the middle, subtruncated obliquely forward 

 above ; hinge of moderate length, forming an angle of about 40° with the 

 umbonal axis. Beaks small, scarcely rising above the hinge, located nearly 

 over the anterior extremity. Surface ornamented by somewhat regular con- 

 centric undulations. 



Length, 2.55 inches ; height, 1.70 inches. 



I have intentionally avoided citing in the synonymy of Mantell's 7. 

 Cripsii, the long list of names representing the wide range of forms most 

 generally regarded as synonymous with that species, because it seems to me 

 that much uncertainty still remains in regard to the relations of many of these 

 shells to the typical I. Cripsii. Indeed, until some one gives a more satis- 

 factory figure and description of that shell than those published by Mantell, 

 it is scarcely possible for any person who has not had an opportunity to 

 examine his type-specimen, or others that have been identified by comparison 

 with it, to form any very satisfactory conclusions in regard to its real char- 

 acters. I certainly cannot see anything in his figure or description from 

 which it can be very positively determined whether his type is a typical 

 Inoceramus (higher than long, with a short hinge), or whether it belongs to 

 the transverse Catillus group. I infer, however, that it belongs to the latter 



