186 PALAEONTOLOGY OF CALIFORNIA. 



SEPTIFER, Recluz. 



S. DICHOTOMUS, 11. S. 

 PL 30, Fig. 2G1. 



Shell small, oblique, subquadrate; cardinal margin straight, 

 anterior and posterior margins subparallel, basal irregularly con- 

 vex ; anterior side abruptly truncated at an acute angle to the 

 rest of the surface. Surface marked, posterior to this angle, by 

 a few large, irregular, radiating ribs, dichotomous, or with smaller 

 ones interpolated. 



Figure, natural size. 



Locality : A single specimen was obtained near Fort Tejon. 



CRENELLA, Brown. 



C. CONCENTRICA, 11. S. 

 PL 24, Fig. 169. 



Shell small, long, narrow, very convex, inequilateral ; beaks 

 prominent, strongly incurved; sides subparallel, the anterior 

 side being most prominent, the posterior curving above gradually 

 into the cardinal margin ; base rounded. Surface polished, and 

 marked by regular, concentric lines. 



Figure, magnified one-third more than natural size. 



Locality: A single specimen, from Division B., at Martinez. 



The distinct, concentric lines, entire absence of radiation, and the more parallel 

 sides, distinguish this species from C. serica, Con. ; and the convex, narrow form, 

 from C. elegantula, M. and H. 



AVICULA, Klein, Lam. 



A. PELLUCIDA, 11. S. 

 PL 25, Fig. 172. 



Shell oblique, subcompressed, broad-linguseform ; ears very 

 unequal ; beaks moderate, anterior ; cardinal line straight ; an- 



