BIVALVES MYTILUS. 69 



MYTILUS Muscle. 



DESCRIPTION OF PLATE XVI. 



Div. I. —Fig. 2. M. pellucidus. Div. VI. Fam. 2. Fig. 6. M. hirundo. 



Div. II Fig. 5. M. discors. Div. VIII. Fig. 3. M. lingua. 



Div. III. — Fig. 1. M. lithophagus. Fig. 4. Interior of Fig. 3. 



Shell bivalve, rough, usually affixed by a byssus or beard of silky 

 fila<:ients ; hinge mostly without teeth, icitli generally a subulate 

 excavated longitudinal line. 



OF the ge mis My tikis forty-six species are enumerated; 

 though some of these are rather 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. 



The hinge of the Mytilus is usually vrithout teeth, 

 having generally in tlieir place a subulate excavated 

 line. Some, however, have small denticulations, with 

 alternate grooves, varying- in different species from ten 

 to fifty; in the M. niger, which has the greatest num- 

 ber, they amount to nearly one hundred. 



A particular class possesses the faculty of penetrating 

 coral and calcareous rocks ; from which, like the Pholas, 

 the shell cannot be extracted without breaking the sub- 

 stance in which it is imbedded. Of this description are 

 the M. lithophagus, M. rugosa, &c. the latter of which 

 is sometimes found in lakes, as well as the sea. 



There are some species which are frequently mis- 

 taken as belonging to the genus Mya; such as the M. 

 latus, M. discors, and M. angulatus; but, by a careful 



