CRETACEOUS FOSSILS. 429 



ANCHUKA (DREPANOCHEILUS) NEBKASCENSIS. 



Plate 12, fig.s. 2, ;5. 



Eostellaria nehraseensiH E. & S., Proc. iVcad. Nat. Sci. Phil., vol. vi, 104. 



Aporrhain nebrascensis (E. & S.) M. & 11., ibid vol. 12, p. 423 ; Gabb, Syiiop. Cret. Foss., 



p., 39. 

 Anchura {Drepotwcheilus) nebrascensis (E. «& S.) Meek, Smithsouiau Check List Invert. 



Foss., p. l!>. 

 Anchura {Drepanocheilns) nebrascensis (E. & S.) Meek, Pal. U. S. Geol. Kept. Ten-., p. 



326, PI. 19, tig. 5. 



Shell small, to moderate size; fusiform, exclusive of the outer lip; 

 spire elevated but moderately robust, about equal in height to the body 

 volution; composed of five or six moderately ventricose whorls, which 

 gradually increase in size; suture line distinct. Outer volution proportion- 

 ally large and bicarinate in the middle; outer lip expanded, and the margin 

 extended in the form of a short, falciform, recurved digitation which is 

 strongly angulated on the back, corresponding to the upper carination of 

 the body volution. The lip is also slightly curved backward and upward 

 near its junction with the spire, forming a deep sinuosity on the inner face. 

 The lower extremity of the body volution is extended in form of a short 

 pointed beak, channeled on the inner face. 



Surface of the shell marked by fine revolving lines and by small ver- 

 tical folds, which are flexuous, and directed forward on the lower part of the 

 volution 



The specimens which we have referred to this species vary consider- 

 ably among themselves, and all seem to be more robust than those figured 

 by Mr. Meek, loc cit. ; still, from their variability, we conclude they are all of 

 the one species. Indeed the species of this entire group are extremely 

 variable, according to the degree of development, especially in the charac- 

 ters pertaining to the aperture and the strength of surface markings, and 

 we are inclined to believe that the same species may often pass beyond the 

 limits of genera, as now recognized. 



Formation and locality. — In Cretaceous limestone on the east fork of 

 Beaver Creek, three miles west of Camp Jenney, Black Hills. 



