182 PALEONTOLOGY OF CALIFORNIA. 



This genus is apparently allied to the group of Megalodon and 

 Opis in the family CrassatcllidcB, the form approaching remotely to 

 31. carinatus; while the hinge differs in all of its details so strongly 

 as to permit no doubts of its generic difference. 



Named in honor of Mr. J. G. Anthony, a gentleman whose 

 name is intimately connected with American fresh-water con- 

 chology. 



A. CULTRIFORMIS, 11. 8 

 PI. 30, Fig. 236, and 236 a. 



Shell long, narrow, compressed, slightly curved and tapering 

 posteriorly; beaks acute, prominent, and placed very near the 

 anterior end, which is obliquely truncated above, regularly 

 rounded below; posterior extremity truncated obliquely up- 

 wards and inwards; cardinal margin concave, basal broadly 

 convex. Surface marked by fine lines of growth, most marked 

 near the beaks, where they assume the character of distinct 

 undulations. 



Figure 236, natural size ; 236 a, a magnified view of the hinge. 

 Locality: Half a dozen specimens, mostly fragmentary; were found by Mr. 

 Mathewson, near Martinez. 



UNIO, Retzius. 



U. PENULTIMUS, n. S. 

 PI. 24, Fig. 164. 



Shell moderately large, subquadrate, compressed, bialate, 

 length and breadth nearly equal ; beaks subcentral (?) ; wings 

 nearly equal in height, the posterior a little the longest, slightly 

 curved on their upper margin and rounded at the ends, so as to 

 unite with the ends of the shell without forming an angle ; an- 

 terior, posterior and basal margins regularly curved, the poste- 

 rior basal portion being more produced than the anterior. Sur- 

 face marked by faint lines of growth, rarely so distinct as to 

 produce ridges. Ligament robust. 



