TERTIARY FOSSILS. 21 



shells, but in adult specimens attain an unusually large size; 

 pallial line unknown. 



From all the characters of the hinge, and the internal position of the ligament, 

 this shell is evidently one of the Mactridce. Its external form, which induced 

 Mr. Esmond to place it in the genus Cardium, has also suggested the generic 

 name. 



P. GABBII. 



PI. 6, Fig. 45, a, b, c, and d. 

 (Cardium Gabbii t Esmond; Proc. Cal. Academy, 1863, vol. 3, p. 13.) 



SHELL large, thick, ventricose, elongated cordate; beaks very- 

 large, strongly incurved and lightly pointed forwards ; anterior 

 end sloping, rounded below, slightly concave above; posterior 

 more or less distinctly truncated; base regularly convex. Lunule 

 broadly cordate, very deeply impressed. Surface irregularly 

 roughened by strong lines of growth. 



Figures, natural size. 



Localities: From the Pliocene, near Kirker's Pass, and rare in the Miocene, 

 south of Martinez ; also in the Sierra Bonita, Monterey County. 



GARI, Schum. 

 STJBGEN. PSAMMOCOLA, Blainv. 



G. (P.) ALATA, n. 8. 

 PI. 5, Fig. 36. 



SHELL oval, thin, compressed, equivalve; anterior end a little 

 the narrowest; beaks small, central; anterior and posterior ends 

 regularly rounded; base broadly convex ; anterior cardinal mar 

 gin expanded into a long narrow ear, marked by one or two ra 

 diating grooves. Hinge composed of two prominent oblique 

 teeth in each valve. Surface marked by a few irregular lines of 

 growth. 



Figure, natural size. 



Locality: From the Pliocene beds near the east end of Kirker's Pass 



