204 
; and however ciosely allied we may acknowledge them to 
be, those genera may be distinguished by having the posterior 
margin arquated somewhat prominently, the apices or beaks not 
being terminal as in Mytillus. The latter naturalist gives the fol- 
lowing account of the animal, Body oval, dilated ) mantle open 
at its inferior middle only, which at its anterior extremity is 
fringed ) foot linguiform, canaliculate, with a byssus at its base 
and many pairs of retractor muscles ; mouth with simple lips ) two 
adductor muscles, of which the posterior one is very small. 
Several species are eatable, and the common Muscle of Europe 
(If. edulis, L.) is taken to market in large quantities for the table. 
All the species are marine with the exception of the M. polymor- 
phus, G-m., or Chemnitzii, which inhabits the Danube and the 
Commercial Docks near London, but which is probably not, strictly 
speaking, of this genus, if we may judge by the somewhat cham- 
bered appearance of the beak cavity. 
They attach themselves by means of their byssus to rocks, 
stones and other fixed bodies, and even to one another. The 
species are numerous ; Lamarck enumerates thirty-seven, of which 
two are fossil, and several have been more recently described. 
Some species are infested by a parasitical Pinnotheres. 
Mytillus hamatus. — Longitudinally grooved; incurved at 
base. 
Mytillus hamatuSy noh. Journ. Acad. Nat. Sci., vol. 2, y>. 265. 
Mytillus striatus, Barnes. 
Ohs. A very common species in the Grulf of Mexico, and is 
carried to the New Orleans market in consequence of its parasitical 
attachment to the common oyster. Hardly a cluster of oysters can 
there be found unaccompanied by one or more and generally nu- 
merous specimens of this shell, in various stages of growth. Our 
figure represents a fine large specimen, in which the incurved tip 
is not so remarkable as in many smaller individuals, and the form 
is somewhat more elongated and less triangular. It seems to ap- 
proach 31. decussatus as described by Lamarck, but in that species 
the transverse striae are stated to be unequal, and its inner margin 
is not said to be of a different color ; a character which in our shell 
is very obvious. Barnes read a description of it to the Lyceum of 
Natural History of New York in 1823, (see Silliman’s Journal, 
vol. 6, p. 364.) 
