The Moon Snail 



35 



but with this difference: the dog is guided by the sense 

 of smell; whereas the moon snail, from the very nature 

 of its surrounding element, is perforce restricted to the 

 sense of taste. In short, the effluvium of its food is 

 carried in the currents of the water, and this latter 

 medium is tasted rather than smelled. 



MUSSEL ATTACHED TO A ROCK. 



In turning to the common prey of the moon snail we 

 find that this bivalve differs as greatly in its habits as 

 in its appearance. It is possessed of two shells, or 

 valves, equal in shape and size. These shells are 

 hinged, and when viewed from the side are slightly tri- 

 angular, are rounded, and are about twice as long as 

 they are w^ide. Sometimes they attain to a length of 

 five or more inches, but more commonly they are three 

 inches long. In the living animal they are dark, almost 

 black, but exposure soon turns them to a pearl gray. 

 Now the mussel is usually content to remain rooted to 

 one spot the greater part of its life, which it does by 

 attaching itself, when young, to any solid object by 

 means of numerous tough silken threads, called byssii. 



