84 



MYTILUS. 



A. Parasitical, affixed by claws. (Plate X. fig. 3.) 



B. Flator compressed, and slightly eared, (fig 4.) 



C. Ventricose, or convex, (fig. 5.) 



Shell rough, often affixed by a thick byssus, or 

 silky beard. Hinge toothless, distinctly marked 

 (except in a few species) with a subulate line, ex- 

 cavated longitudinally. Shape either folded, crested, 

 lobed, or attenuated towards the apex. 



The Mytili, though not all absolutely parasitical, 

 or inseparably attached to other substances, are 

 all rendered stationary by some mode or other of 

 adherence : the silky filaments emitted by some 

 species, are entwined in the corallines and stones 

 at the bottom of the sea, and securely anchor the 

 groups of muscles which are found there. Some 

 perforate the rocks, and larger shells, and form 

 to themselves a habitation, from which, like the 

 Pholades, they possess no means, nor perhaps in- 

 clination, to escape. 



The word Mytilus is, perhaps^ derived from jw-Zrof, 

 a thread or wel. 



