106 CLASS ACEPHALA. 
which extends along its whole length. 'The animal (LIM- 
NA, Poli,) has no byssus; its foot, which is very large, 
compressed, and almost quadrangular, enables it. to crawl 
upon the sand or ooze. The posterior extremity of its mantle 
is provided with numerous small tentacula. ‘The anodontes 
inhabit fresh water. 
Several species are found in France, one of which, (mytilus 
cygneus, Lin.) very large, is common in ponds, &c. with oozy 
bottoms. Its light and thin shells are used for milk-skimmers, 
but its flesh is not eaten in consequence of its insipidity. Add 
M. Anatinus, Chemn., &c. 
An oblong species, in which the hinge. is granulated 
throughout its entire length, is distinguished by M. de La- 
marck under the name of IR1ipINA (Jrid. exotica, Encyc. 
Method.) ; the hind part of its mantle is somewhat closed. 
And Dr. Leach distinguishes by the term DIPSADA ano- 
ther, which has its angles more decided, and in which there 
is a vestige of a tooth upon the hinge. 
Unio, Brug., 
These mollusca resemble the anodontes, both in their animal 
and shell, with the exception of their hinge, which is more 
complex. ‘There is a short cavity in the anterior part of their 
right valve which receives a short plate or tooth from the left 
one, and on its posterior part is a long plate, which inserts 
itself between two others on the opposite side. They also 
inhabit fresh water, preferring running streams. 
Sometimes the anterior tooth is more or less stout and un- 
equal, as in 
Mya margaritifera, L., a large thick species, the mother- 
of-pearl of which is so beautiful, that its concretions are used 
in dress as pearls. Found in France, as is the 
Unio littoralis, Lam., a smaller and square species. 
