548 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [1885. 



Venus (Chione) fluctifraga Sby. 



The commoD cockle; often collected for food, and excellent quality. 

 This and the two following species, which are less abundant, are often 

 pearl-bearers : 

 Venus (Chione) succiucta Val. 



Mui Diego. 

 Venus (Chione) simillima Sby. 



San Diego. 

 Tivela crassatelloides Cour. 



A market clam but not in very plentiful supply. This is sometimes 

 pearl-bearing. 

 Cytherea undato-stiiata Cpr. 



Dead valves only have been found of this; San Diego Bay. 



Cytherea (Amiantis) callosa Cour. 



This beautiful species is rarely found at San Diego, but is abundant 

 on Todos Santos Bay, where it burrows in the hard, sandy beach to a 

 depth of about a foot near very low- water mark, where it is easily ob- 

 tained for the market by Indians whenever it may be in demand. 

 Tapes stamiuea Cour. 

 Tapes staminea Cour. var. tumida Sby. 



San Diego. 

 Tapes staminea Cour. var. diversa Sby. 



San Diego and Todos Santos Bay. 

 Tapes laciniata Cpr. 



San Diego and Todos Santos Bay. 

 Cardium quadragenarium Conr. 



La Pla>a; rare. Odd valves abundant at Todos Santos Bay. 



Xiiocardiuni elatum Sby. 



isot rare, below low-water mark on the muddy flats of San Diego 

 and F^lse Bays. Also Todos Santos Bay. 

 liiocardium substriatum Conr. 



Abundant with the last. 

 Chama exogyra Cour. 



Abundant on all rocky beaches at low water. 

 Chama spinosa Sby. 



Less abundant, frequenting deeper water. 



Lucina nuttallii Conr. 



San Diego. • 



Lucina californioa Cour. 



San Diego. 

 Diplodonta orbella Old. 



Found in holes in rocks or in dead bivalves at La Playa; not rare. 

 Also Todos Santos Bay. A single example of a much flatter species 

 was found at San Diego, which is now in the collection of the Phila- 

 del})hia Academy of Sciences. 



