BIVALVES MYTILUS. 45 



Margaritifeius is renowned for the iridescent colors it 

 displays, and is, moreover, famous for the tine and valu- 

 able pearls it engenders within its silvery valves. The 

 young shells of this species, are sometimes so different 

 to the adults in appearance, that they can scarcely be 

 recognized for the same. Some of this genus possess 

 the faculty of penetrating and eating away coral-rocks, 

 hard marble, and limestone; into which they insinuate 

 and immure themselves so artfully, that it becomes ne- 

 cessary to break the stone before there is a possibility 

 of withdrawing the shell and its inhabitant. Of this 

 description are the Mytilus Lithophagus and Rugosus. 

 The latter is sometimes found in lakes, as well as seas. 



There are some muscles, which, on a superficial glance, 

 might be mistaken as belonging to the genus Mya; such 

 are the Mytilus Versicolor, Discors, and Afer; but, by a 

 minute inspection of the hinge, the error would soon be 

 discovered. The general appearance of Muscles differs 

 greatly, some being perfectly smooth, and beautifully 

 marbled and variegated with fine coloring; others are 

 elegantly radiated with purple and white, like a tulip ; and 

 some again are coarsely ribbed and grained with minute 

 tubercles, making the shell quite rough, and of one color 

 only, such as black, blue, green, yellow, and brown. 

 But they are most of them indebted to their epidermis 

 for whatever outward color they may possess; which, 

 when removed, often presents so different a surface, that 

 even an adept might be puzzled to recognize two shells 

 of the same species. Some of the cuticles or skins are 

 often bearded or shaggy, and, in some instances, the valves 

 gape, as in Mytilus Bilocularis, and other similar species. 



However, almost the whole of the different species of 

 Muscles, seem to accord with the habits of the common 

 or eatable Muscle (Mytilus Edulis), wi:ichhivariably af- 



