MUSSELS. 47 



to circumstances. It soon looses its regularity 

 of form, and becomes oyster-shaped ; sometimes 

 developing one valve and sometimes the other, 

 as opportunity offers; twisting itself to the right 

 or left, and becoming so distorted that it seems 

 to have wholly forgotten its youthful grace. In 

 color, it varies from yellow to brown, on the out- 

 side; while within, it is pure white, with a rich 

 purple area at the hinge line. This purple color 

 is very permanent, and fragments of shells may 

 often be found, still showing it; the ligament is in- 

 ternal, in a deep, narrow pit; the muscular im- 

 pression is smooth, and very large. This species 

 sometimes grows to the size of a large oyster; it 

 is occasionally cast up alive from d^ep water, 

 but dead shells are much more common. 



The last shell of this group which we shall 

 mention is Lima orientalis, Ad. & Pve., File- 

 shell, an inside view of which is shown in Fi^. 

 5, PI. XII. This little shell is pure white, and 

 is thrown up from the sea attached to sea-weed. 

 The valves are obliquely oval, thin, gaping, and 

 sculptured like a file ; length, three-fourths of an 

 inch. 



Mytilus edulis, Linn., is the common mussel, 

 known to every one. Spinning its strong, horny 

 byssus, it attaches itself to rocks, posts, and 

 wharves, in countless numbers. Its smooth, dark 

 purple shell and orange colored soft parts are 

 too well known to need description. The com- 

 mon length is two inches. 



Mytilus Calif omianus, Conr., Fig. 6, PI. 

 XII, is found covering the rocks over Avhich the 

 breakers dash the wildest. Moored by its strong 



