CALIFORNIA FISH AND GAME. 113 
THE MUSSELS OF THE PACIFIC COAST.* 
By EDWARD P. RANKIN. 
To most of those who have spent any time on the seashore, the 
mussels, clustered in balloon-shaped masses on the pilings of wharves or 
scattered in irregular groups on the rocks, are a familiar sight. It is 
the purpose of this paper to make these mussels more widely known, to 
introduce them to those people who have had no opportunity to make 
their acquaintance at first hand, and to make them, if possible, more 
interesting to those who have met them already. 
We have, on the Pacific coast, two species of mussel: a small one, 
Mytilus edulis, and a large one, M. californianus. The latter-named 
Fig. 59. Two common species of mussels found in California. Left, Mytilus californianus, 
a large form found along the entire coast; right, Mytilus edulis, a smaller variety restricted 
more largely to inlets and bays. Photograph by W. C. Mathews. 
species, which can attain a length of ten inches, is known from Socorro 
Island (in the Revilla Gigedo group, about 250 miles south of Lower 
California) to Alaska; its shell has both radial and concentric markings, 
and varies in color from light brown to dark purple. This mussel likes 
the salt water of the open coast, where it clings to reefs and wharves. 
M. edulis rarely exceeds three inches in length and has a shell that is 
smoother (lacking the radial lines) and darker than that of califor- 
nianus. It ranges from San Diego northward and prefers the more 
sheltered and brackish waters of inlets and bays such as San Diego Bay 
and San Francisco Bay. 
*Printed by permission of the United States Bureau of Fisheries. 
