CRETACEOUS FOSSILS. 103 



This species agrees so closely with Dr. Shumard's description of V. Navarroensis 

 (Proc. Boston Soc. of Nat. Hist., Sept., 1861), that I have called it by his name. 

 One specimen of the same length as his, 3.72 inches, is .2 inch wider in the body 

 whorl, and with a length of aperture .2 inch greater. This slight variation would 

 of course not separate it. There is a very slight discrepancy in the surface- 

 markings, but not more than might be expected. The plain ribs at the top of the 

 whorl arc always more numerous than in his description, and I have not been 

 able to find on any specimen more than seventeen of the revolving ribs in all. 

 The greater number of volutions can easily be accounted for by the larger size of 

 the specimen figured. 



Should my determination of this species be correct, it will be an interesting 

 link between the Cretaceous deposits on the two sides of the continent, associated, 

 as it is, in Texas, with many species, the position of which, in the formation, has 

 been satisfactorily determined east of the Mississippi. 



MITRA, Lam. 



M. CRETACEA, n. 8. 

 PI. 28, Fig. 215. 



SHELL small, elongated, subfusiform ; spire high ; whorls seven 

 and a half or eight, angulated, sloping on the upper margin, 

 slightly sinuous below. Aperture long, rather narrow ; columella 

 with four (or live '?) oblique folds. Surface marked by very fine 

 revolving lines and indistinct lines of growth. Anterior extremity 

 of the shell unknown. 



Figure, three times natural size. 



Locality: A single specimen from Martinez ; Mr. Mathewson. 



WHITNEYA, N. Gen. 



SHELL pyriform, spire low, suture channelled. Mouth with a 

 well-marked notch posteriorly; outer lip simple, canal twisted 

 and emarginate at the extremity; columellar lip incrusted, and 

 with two or more very oblique folds below, like those of Fascio- 

 laria. 



This genus resembles in most of its characters Fasciolaria, although its tout 

 ensemble is different from any species of that genus with which I am acquainted. 



