OTHER BIVALVE MOLLUSKS 



101 



three inches. I found them abundant at Bolinas, 

 and they reach as far south as San Diego. 



The shell of the little Saxicava arctica^ Linn., the 

 Arctic Saxicave, is small, thin, wrinkled, and irregu- 

 lar. The beaks are near the front ot the shell, which 

 is abruptly terminated. Ligament small, external, 

 behind the beaks. Color ashy white, length from 6 

 to 12 mm. It is found on the holdfasts of kelp and 

 in similar situations. By some this form is consid- 

 ered to be but a variety of ^. pholadis^ Linn., a small 

 species which has been dredged in San Pedro Bay. 

 Saxicava rugosa^ Linn., the Rough Saxicave, occurs 



Fig. 79 



in the far north, and also as far south as San Diego. 

 I believe all three are but varieties of one species. 



Panopaa generosa^ Gld., the Giant Panopsea, is 

 shown in Figure 79. This huge mollusk, which lives 



