BIVALVES. — MYTILUS. 



MYTILUS.— Muscle. 



Am77ial allied to an Ascidia : Shell bivalve, rough, gene- 

 rally affixed by a hyssus or heard of silky filaments ; hinge 

 mostly without teeth, with generally a subidate, excavated 

 longitudinal line. 



OF the genus Mytilus tliere are enumerated forty-six 

 species; though some of these are a Httle indistinct in char- 

 acter, yet the greatest proportion of them bear a near al- 

 liance to the general form and habits of the common or 

 eatable muscle. There are, indeed, a few exceptions, such 

 as the M. margaritiferus (tnie mother-of-pearl shell), and 

 others of a similar description ; some of which we have re- 

 moved from the position they occupied in this genus in the 

 former editions of the present work, into the third family 

 of the fourth division of the Ostrea genus, as they exhibit 

 strong evidence of belonging to that 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 denticvJations 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 colouring; others are elegantly radiated 

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

 coarsely ribbed and gi'ained with minute tubercles, and of 

 onecolovir only, such as black, blue, green, yellow, or brown. 

 Most of them are indebted to their epidermis for whatever 

 outward colour they may possess ; when this is removed, so 

 different a surface is often presented, that even an adept 



