422 GEOLOGY OF THE BLACK HILLS. 



remarks tluit it differs from the former in the flexuous character of the 

 vertical folds, and from the latter by the possession of only one, instead of 

 several, plaits on the columella. 



This species was originally described by Messrs. Hall and Meek under 

 the name RosteUaria fusiformis, and subsequently placed with doubt under 

 the genus Gladius by Meek and Hayden, with the new specific name Chey- 

 ennensis, as the name fusiformis had been previously used by Mons. Pictet 

 and Roux for a species of RosteUaria, and by Valenciennes for a species of 

 Fasciolaria. But as Mr, Meek has subsequently proposed a new subgeneric 

 name, with this species as the type, it will necessarily revert back to the 

 original specific name fusiformis if the new subgeneric name Cryptorliytis 

 is to be adopted. We have, therefore, thus referred it. 



Formation and locality. — In limestone of the Fort Pierre Group, on the 

 Cheyenne River, near Rapid Creek, Black Hills. 



FASCIOLAEIA (CRYPTOEHYTIS) CONTORTA. 



PlatP 12, fig. 10. 



Fnsiis contortns M. & H., Proc. Acad. Nat. Sci. Phil., voL 8, p. 65. 

 Pleuroiomaria contorta M. & H., Proc. Acad. Nat. Sci. Phil., vol. 12, p. 185. 

 Turris contorta M. & H., ibid., 422 ; and Meek, Sinitlisoniau Check List luvert. Foss.,p.22, 

 Turris {Surculaf) contorta (M. & H.) Meek, Pal. U. S. Geol. Smv. Terr., p. 385, PI. .31, 

 fig. 7. 



Shell fusiform, spire elevated, number of volutions not determined 

 (5^—6 Meek), but rapidly increasing in size with the increased growth of 

 the shell, ventricose and obtusely angulated in the middle, the outer one 

 more rapidly increasing on the aperture side. Volutions marked on the 

 angulation by strong, distinct, vertical costa or folds, which do not quite 

 reach the suture above or below; about twelve of them have occupied the 

 outer volution on the largest specimen. Aperture long-pyriform, narrowed 

 below and extended into the moderately long, slightly twisted canal. 

 Columellar lip twisted, and marked by a single distinct, very oblique fold, 

 which is situated above the middle of the leng-th. Surface unknown. 



The examples of this species in our possession are internal cast, with 

 j)()rtions of the shell remaining only as a white calcareous powder, easily 

 removed ; and by breaking the larger figured example and brushing away 



