Of the
rest, some are bivalved and some univalved; and by 'bivalves' I mean
such as are enclosed within two shells, and by 'univalved' such as are
enclosed within a single shell, and in these last the fleshy part is
exposed, as in the case of the limpet. Of the bivalves, some can
open out, like the scallop and the mussel; for all such shells are
grown together on one side and are separate on the other, so as to
open and shut. Other bivalves are closed on both sides alike, like the
solen or razor-fish. Some testaceans there are, that are entirely
enveloped in shell and expose no portion of their flesh outside, as
the tethya or ascidians.
Again, in regard to the shells themselves, the testaceans
present differences when compared with one another. Some are
smooth-shelled, like the solen, the mussel, and some clams, viz. those
that are nicknamed 'milkshells', while others are rough-shelled,
such as the pool-oyster or edible oyster, the pinna, and certain
species of cockles, and the trumpet shells; and of these some are
ribbed, such as the scallop and a certain kind of clam or cockle,
and some are devoid of ribs, as the pinna and another species of clam.
Pages:
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183