70 



MYTILUS. 



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



B. Flat or compressed, and sliglitlyeared. (fig. 4.) 



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



Shell rough, often affixed by a thick byssus, oi* 

 silky beard. Hinge toothless, distinctly marked 

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

 cavated longitudinally. Shape either folded, crest- 

 ed, lobed, or attenuated towards the apex. 



The Mytili, though not all absolutely parasitical, 

 or inseparably attached to other sul)stances, are all 

 rendered stationary by some mode or other of ad- 

 herence : the silky filaments emitted by some 

 species, are entwined in the corallines and stones 

 at the bottom of the sea, and securely anchor tho 

 groups of muscles which are found there. Some 

 perforate the rocks, and larger shells, and form to 

 themselves a habitation, from which, like the Pho- 

 lades, they possess no means, nor perhaps inclina- 

 tion, to escape. 



The Pearl-bearing shell of the Indian fisheries 

 is the Myiilus margaril'iftrus: it is most abundant 



