[9] OYSTER CULTURE 761 
surrounded by tactile appendages, the palps, which seem intended to 
take the place of the organs of sight and touch. From each side of the 
body hang two folds of integument, formed of a double membrane, which 
clothe the inner surfaces of the shell, protecting the body of the animal 
from immediate contact with the hard external covering, and guarding 
it from any rubbing that might take place if in contact with such a sur- 
face. These protecting folds form the mantle, which also secretes the 
shell. 
Some species, the mussels among others, possess a sort of fleshy foot, 
which can be protruded at will from between the valves of the shell and 
the folds of the mantle, and can also aid'in locomotion. But the greater 
portion of the acephalous mollusks live firmly attached to solid objects 
under the water, either by a union of the calcareous matter of their 
Shells with the object upon which they are stationed, or by means of a 
small bunch of hair-like threads, which arise from near the ligament 
uniting the valves, and which are called collectively the byssus. Other 
species live buried in the mud, or move about in the water, sometimes 
swimming great distances. They are met with in the fresh water of 
our rivers and lakes, and in all salt water. 
THE OYSTER. 
Naturalists have united under the common name of oyster a large 
number of mollusks having very different aspects; they are the genera 
Gryphea, Plicatula, Vulsella, Malleus, Lima, Meleagrina or pearloyster, 
&c.. These mollusks are widely distributed, and have been very abund- 
ant in both fresh and salt water, in all ages of the world, so much 
so that they have left some very extensive fossil remains, as in the 
cretaceous beds of Versailles, of Meudon, and in all of those deposits 
to which, from their marine origin, the name of Neptunian beds has 
been given. Without entering, however, into useless details in re- 
gard to the various species of this family—since as articles of food they 
are of little or no interest—we will confine our attention to the edible 
oyster (Ostrea edulis), which is easily recognized by its compressed, 
roundish body and bivalve shell, the two valves of which are quite 
unlike, one being nearly flat, the other convex, and both without teeth 
at the hinge joint. The two valves are formed of a series of imbricating, 
circular layers of carbonate of lime secreted from the mantle, and are 
held together and closed by a single large and powerful adductor mus- 
cle, attached near the center of each valve. The layers of shell material 
have very much the appearance of shingles upon the roof of a house. 
The best-known forms of this animal are the common oyster, used upon 
our tables; the horse-foot oyster (Ostrea hippopus), very large and broad, 
but little esteemed, found at many places along the shores of the Medi- 
terranean, and also at Bologne-sur-Mer; the oyster of Beauvais (Ostrea 
bellovacina), taken at Bracheux, near Beauvais, &c. But the oyster is 
so well known to every one that, without attempting a minute descrip- 
