180 PALAEONTOLOGY OF CALIFORNIA. 



ERIPHYLA, N. Gen. 



Animal unknown. Shell subtrigonal. Surface of valves con- 

 centrically ribbed or striated. Hinge composed of two primary 

 teeth in the right valve, and one in the left, and an anterior and 

 posterior lateral tooth in each valve. Ligament external ; lunule 

 deep. Pallial line unknown. 



This shell is closely allied to Astarte and Gouldia, but differs 

 from both, in the presence of a well-marked posterior tooth in 

 each valve. On the left valve there is a rudiment of a second 

 cardinal tooth, which enters a depression on the opposite side, 

 behind the large, posterior, cardinal tooth of that valve. Other 

 species may show two well-defined cardinal teeth on each side. 



E. UMBONATA, 11. S. 

 PI. 24, Fig. 162, and 1G2 a. 



Shell subtrigonal, inequilateral; beaks prominent, subcen- 

 tral, inclined in advance ; posterior cardinal line rapidly sloping 

 convexly ; basal half of the shell nearly semicircular ; anterior 

 end rounded, excavated under the beaks. Lunule profound, 

 subcordate. Internal margin with a minute rim or thickening 

 running parallel with the edge. Surface ornamented with nu- 

 merous regular concentric ribs, which, in some specimens, 

 become obsolete on the middle of the shell. 



Figure 162, natural size; 162 a, magnified view of the hinge. 

 Localities: Cow Creek, Shasta County; also Curry's, south side of Mount 

 Diablo (Division A.). 



