217 
those which are of an elongated form, and have a groove or line 
running along the disk of the valve, from which the folds part on each 
side, like the teeth of a comb. 
Under the first of these sub-divisions may be placed 0 . diluviana, 
Linn, which is a shell as large, and even larger, than the common 
oyster, being plicated, and having the margin formed by acute-angled 
teeth, like those of a saw, and placed at right angles with the surface 
of the shell : the margin being finely striated by the apposition of the 
different lamellae. A small specimen of this species is represented 
Plate XV. Fig. 1. Shells very nearly, if not exactly, agreeing with 
these fossils, have lately been found in the South Sea. O. crista galli, 
the fossil cockscomb oyster, appears to be of this same species. O. 
Jlabellula, Lam. is oblong, cuneiform, slightly bent, with long rough 
plicae : the upper valves flat. This shell much resembles Chama 
plicata altera , Brand, and there also exists a considerable agreement 
in the hinge ; for, on a superficial view, the hinge of this shell would 
be supposed to be that of a Chama : the cartilage pit is very oblique 
and deeply sunk, giving much of the appearance of the receptacle of 
the oblique tooth of the Chama. 
The shells of the second subdivision have very much the appearance 
of a leaf. Such is the fossil oyster from France, Plate XV. Fig. 4, in 
which the shell, although now perfect stone, retains its original surface 
and shelly lustre. This species, O.frons vel folium, is known to the 
continental oryctologists as La feuille de laurier. 
Plate XV. Fig. 2, is a beautiful and rare French fossil of this sub- 
division, they being hardly ever found in so perfect a state. This shell 
is also known as a Crete du Coque, or crista galli ; and it must, per- 
haps, be admitted, that this appellation applies better to its form than 
to that of any of the preceding shells. This specimen enables us to 
form a true notion of the shape of the shell, which has not yet been 
correctly shown. 
VOL. III. 
F F 
