CRETACEOUS FOSSILS. 203 



L. appressa, n. s. 



PI. 31, Fig. 271. 



Shell thin, flattened, elongated, irregularly oval ; anterior mar- 

 gin straight, or very slightly convex ; posterior irregularly curved, 

 most prominent in the middle; ears unequal. Surface marked 

 near the base by a few faint, radiating undulations, crossed by 

 fine lines. 



Figure, natural size. 



Localiiy: San Luis Gonzaga Eaneh (Division A.). A single cast retaining but 

 a small portion of the shell. 



PLICATULA, Lam. 



P. VARIATA, 11. S. 

 PI. 2G, Fig. 190. 



Shell variable, usually somewhat curved. Lower valve attached 

 by a portion of the surface, deep, radiately costate, ribs occa- 

 sionally dichotomous. Upper valve flat or concave, plicate like 

 the lower, but not so strongly, the ribs being sometimes obsolete. 

 Hinge robust ; muscular scar large ; internal margin of the upper 

 valve crenate ; lower valve marked with pits corresponding with 

 the teeth above. 



Average length, about .7 inch. 



Localiiy: Abundant in a hard, gray, calcareous sandstone, from Battle Creek, 

 Shasta County (Division A.). 



This little shell is extremely variable in outline and convexity; one of the com- 

 monest forms is illustrated in the figure. 



ANOMIA, Linn., Mull. 



A. LINEATA, 11. S. 

 PI. 26, Fig. 193. 



Shell thin, variable in shape; commonest form subcircular, 

 often obliquely truncated on the right side ; beak of upper valve 



