48 
CALIFORNIA SEA SHELLS. 
anchor, it enjoys the rush of air and water, and 
fears no danger. This species can easily be dis- 
tinguished from the last by its brown, glossy 
epidermis and conspicuous ribs. The shell is 
purple, but more or less whitish. Some old 
specimens, with nearly obsolete ribs, grow to a 
length of eight or ten inches. The soft parts 
are orange colored, and are frequently eaten. 
Resembling the mussels are the Modiolas, 
several species of which are found on the coast. 
The shells are bulged near the hinge line, and 
extend beyond the umbo on one side. Modiola 
capax , Conr., is covered with a glossy, bro.vn* 
epidermis, mossy in parts. The animal binds 
itself by a strong byssus, and seems to seek se- 
cluded places under stones, where it can be found 
at low tide. Modiola recta , Conr., is “ long, 
thin, narrow and angular, with chaff-like hairs.” 
Among the difficult things to explain is the 
fact that a mollusk, with a thin, flexible shell, 
can bore a deep hole into hard rock. That this 
is done, however, can be proved bv any one who 
will examine the work of the Pea-pod Shell, 
Adula falcata, Gld., Fig. 1, Pl. XIII. The 
shell is long, narrow and slightly curved ; the in- 
side is white and pearly, while the outside is cov- 
ered with a dark chestnut epidermis, which has 
numerous transverse wrinkles. I found the rocks 
of Daxbury Reef, at Bolinas, almost alive w T ith 
this and other borers. The deep, narrow holes 
are curved to fit the shell, and the animal also 
spins a byssus, which it attaches to the sides of 
its burrow ; length, two inches. Adula stylina , 
