OTHER BIVALVE 
Periploma discus, 
Stearns, the Round Lan- 
tern-shell, is well shown 
in Figure 87. This fine 
species was discovered 
at Long Beach, Cal., not 
many years ago, and for 
a time specimens were 
very rare. The shells 
are white, exceedingly 
thin and fragile, almost 
eircular, though with 
one square corner. The 
diameter of large speci- 
mens is nearly two 
inches. 
MOLLUSKS 99 
Fig. 87, (*) 
A delicate little shell, 
of which Figure 88 rep- 
resents a large specimen, 
found at various points 
along the coast and also in 
San 
Francisco Bay, is 
named Lyonsia californica, 
Conr., the California Lyonsia. The shell is bulged 
at one end, while at the other it is narrow, thin and 
crooked. The outer coat shows many concentric 
striw, but this is easily rubbed off, revealing the 
inner layer, which is quite pearly. 
