VENUS SHELLS, 2h 
hinge are approximated beneath the beak in a single 
group. In general they are more flattened and 
wider in proportion to their length than the Cockles, 
from which they differ conspicuously also in having 
the ribs never radiating towards the margin from 
the beaks, but always, where present at all, in con- 
centric lines parallel to the margin. The ligament 
often leaves behind the beaks an oval depression, 
commonly called the corslet. The muscular im- 
pressions are strongly marked, and the pallial, or 
that which indicates the adhesion of the mantle, is 
much sinuated in its course. 
The animal has two siphonal tubes, capable ot 
being protruded in a greater or less degree, some- 
times united to each other; their extremities are 
fringed, though very slightly in some species. The 
mantle is widely open in front, for the projection of 
a large compressed foot, which serves for creeping. 
This family is peculiarly rich in the number of 
its species; the genera Venus and Cytherea alone 
contain about a hundred each still existing, be- 
sides half as many more which are fossil. They 
are found in almost all seas, generally at a moderate 
distance from the shore, but extending from tide- 
marks to great depths. Our native species, Venus 
striatula and ovata, for example, live indifferently 
at low-water mark, and at the depth of a hundred 
fathoms. ‘The tropical regions afford, as usual, the 
greatest number of species, and those most remark- 
able for beauty of form, sculpture, and colour, for 
all which, however, the majority of the family 
may be considered as preeminent among bivalves ; 
whence the various appellations of the goddess of 
beauty, and similar names have been selected for 
the genera. 
