CRETACEOUS FOSSILS. 181 



CRASSATELLA, Lam. 



C. GRANDIS, 11. S. 



PI. 24, Fig. 1G3. 



(Crassatella alta, Con. Pacific R. R. Report, vol. 5, p. 321.) 

 (Not C. alia, Con. Tert. Foss, p. 21, pi. 7.) 



Shell very large, subtrigonal, a little longer than wide; 

 beaks moderate in size, prominent, with the sides sloping 

 rapidly, most abrupt in advance, slightly convex behind ; ante- 

 rior end broadly rounded; posterior rounded, subtruncated ; 

 base nearly straight, and sloping upwards from directly below 

 the beaks to the posterior end ; umbonal ridge faint, broad, 

 rounded. Surface marked only by a few small lines of growth. 

 Inner margin minutely crenulated. 



Figure, natural size of a small perfect specimen. One cast, with a portion of 

 the shell preserved, measures over four inches from beaks to base. 



Localities: From Division B., near Clayton; also from Alizos Creek, near 

 Canada de las Uvas. 



This species was referred to C. alta, by Mr. Conrad, from fragments. I have 

 been fortunate enough to procure two casts at the same locality, one of which still 

 retains a large portion of the shell ; and have before me a perfect specimen, 

 although small, found by Mr. Re"mond near the Mount Diablo coal-mines. The 

 specific distinctness is obvious on comparing the outline of fig. 1G3 with plate 7 

 of "Tertiary Fossils." The shell is thicker than in C. alta, and the pallia! im- 

 pression is much more nearly parallel with the margin of the shell, wanting 

 almost entirely the abrupt recurve posteriorly. The ligament area runs out gra- 

 dually below, instead of ending abruptly ; and the hinge-plate is equally massive, 

 and even broader than in Mr. Conrad's species. 



ANTHONYA, N. Gen. 



Shell equivalve, very inequilateral, long, narrow; beaks an- 

 terior, nearly terminal. Hinge composed of two strong, oblique 

 teeth in each valve; those in the right valve articulating in front 

 of those in the left. Muscular scars and pallia! line unknown. 



