INVERTEBRATE PALuEONTOLOG V. 365 



ing open some masses of rock since the plates were engraved, and are con- 

 sequently only illustrated here by the annexed wood-cut. It will be readily 

 distinguished from all of the foregoing species by the three stronger, less 

 oblique plaits of its columella, as well as by its smaller, more numerous, and 

 straighter vertical costse. In general form, the direction and position of the 

 plaits of its columella, and in its vertical costa?., it more nearly approaches 

 Fasciolaria assimilis, Stoliczka (Paleeont. Iudica, II, pi. x, fig. 7), but still it 

 differs, not only in its smaller size, but also in having less convex volutions, 

 a narrower and straighter canal, and a differently-formed aperture. It .seems 

 to be also allied to Mitra cancellata, Sowerby, as illustrated by d'Orbigny on 

 plate 221 of the Paleont. France, II, Terr. Cre't., but differs in its volutions, 

 being more compressed above, and its aperture consequently more acutely 

 angular posteriorly; while its vertical costse are larger and much less numer- 

 ous, and its revolving striae much finer. The plaits of its columella also do 

 not extend across the inner lip, as represented in that species. 



I am' not at all satisfied, as already stated, with the reference of this 

 shell to the genus Fasciolaria, owing to the fact that the plaits of its colu- 

 mella are stronger, and much less oblique, and occupy so much higher a 

 position than in Fasciolaria proper. I do not believe, however, that such 

 shells can be properly referred to any section of Mitra or Tarricula, as is 

 sometimes done. 



Locality and position. — Yellowstone River, 150 miles from its mouth; 

 from beds containing a blending of the fossils of the Fort Pierre and Fox 

 Hills groups of the Upper Missouri Cretaceous series. 



? Subgenus CRYPTORHYTIS, Meek. 



Fasciolaria? (Cryptorhytis) C h e ye u n e n s i s, M. & H. (sp.). 



Plate 19, figs. U, a,b. 



Eostellaria fusiformis, Hall and Meek (1854), Mem. Am. Acad. Arts and Sci. Boston, V (new ser.), 3SKJ, pi. iii, 

 fig. 10 (not It. fusifnrmis, Pictet and Rous, 1848; or Fasciolaria fiisiformis, Valen- 

 ciennes). 



Gladias ? Cheyennensis, Meek and Hayden (18150), Pr ceed. Acad. Nat. Sci. Puila., XII, 42-2.— Meek (1864 , 

 Smithsonian Check-List N. Am. Cret. Fossils, 20. 



Shell fusiform* very thin; spire acutely elevated; volutions about six, 

 convex, increasing gradually in size, last one moderately gibbous around the 

 middle, atid contracting rather rapidly into the straight canal below; suture 

 deep, with a kind of constriction or furrow just below it; aperture rhombic- 



