70 
M Y T I L U S. 
A* Parasitical, affixed by claws. (Plate X. Fig. 3.) 
B. Flat or 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, 
excavated 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 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 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 Pho- 
lades, they possess no means, nor perhaps inclina- 
tion, to escape. 
The Pearl-bearing shell of the Indian fisheries 
is the Mytilus margaritiferus : it is most abundant 
