62 BIVALVES. — MYTILUS. 



MYTILUS.— Muscle, 



Animal allied to an Ascidia: Shell bivalve, rough, gene- 

 rally affixed hy a byssus or beard of silky filaments; 

 hinge mostly without teeth, with generally a subulate, 

 excavated longitudinal line. 



Of the genus Mytilus there are enumerated sixty-four 

 species; though some of these are a little indistinct in 

 character, yet the greatest proportion of them bear a near 

 alliance to the general form and habits of the common or 

 eatable muscle. There are, indeed, some exceptions, 

 such as the M. crista -galli (cock's-comb oyster), and the 

 M. margaritiferus (true mother-of-pearl shell,) and others 

 of a similar description; most of which give strong evi- 

 dence of belonging to the Ostrea, rather than the Myti- 

 lus genus. 



The hinge of the Mytilus is usually without teeth, hav- 

 ing generally a subulate excavated line in place of them. 

 Some species have, however, little denticulations with al- 

 ternate grooves, which vary in number from ten to fifty; 

 in the M. niger, which has the greatest number, they 

 amount to one hundred. 



The general appearance of muscles differs greatly, some 

 being perfectly smooth, and beautifully marbled and va- 

 riegated with fine coloring; others are elegantly radiated 

 with purple and white, like a tulip; and some again are 

 coarsely ribbed and grained with minute turbercles, and 

 of one color only, such as black, blue, green, yellow, or 

 brown. Most of them are indebted to their epidermis 

 for whatever outward color they may possess; when this 



