90 WEST AMERICAN SHELES 
Figure 80 gives us 
a good idea of the 
shell of Platyodon 
cancellatus, Conr., the 
Flat-tooth Clam. It 
closely resembles the 
Mya, but its broad 
hinge-tooth is not so 
large; moreover the 
valves are much thicker and firmer, and are greatly 
bulged. The shell is white or gray, and the length 
is two or three inches. I found them abundant at 
Bolinas, and they reach as far south as San Diego. 
The shell of the little Saxicava artica, Linn., the 
Arctic Saxicave, is small, thin, wrinkled and irreg- 
ular. The beaks are near the front of 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 roots 
of kelp, and in similar situations. By some this 
is considered but a variety of S. pholadis, Linn., 
a small species which has been dredged in San 
Pedro Bay. Sawicava rugosa, Linn., the Rough 
Saxicave, occurs in the far north, and also as far 
south as San Diego. I believe all three are but 
varieties of one species. 
Panopea generosa, Gld., the Giant Panopza, 
(Glycimeris generosa), is shown in Figure 81. This 
huge mollusk, which lives chiefly in northern 
waters, is the king of all the burrowing clams. 
A pair of shells, kindly sent me from Puget Sound, 
Ly) i 
EB Ri NN} 
