84 
MOLLrSCA. 
SpHiERULiTES Lamet/i., 
Whei’e the valves are roughened l)y irregularly raised plates. It 
is also thought we may add the 
Calceola, 
One valve of which is conical but free, and the other flat and even, 
somewhat concave, so that they remind us of a shoe ; and even the 
Hifporites, 
Where one valve is conical or cylindrical with two obtuse, longi- 
tudinal ridges on the inside ; the base even appears to be divided into 
several cells by transverse septa*; the other valve fits like a cover. 
The 
Batolithes, Montf. 334, 
Are cylindrical and straight Hippurites ; they are frequently found 
greatly elongated. There is much incertitude, however, with respect 
to all these bodies f. 
As to the well known living testaceous Acephala, Linmeus had 
united in the gen\is 
OsTREA, Lin., 
All those which have but a small ligament at the hinge, inserted 
into a little depression on each side, and without teeth or projecting 
plates. 
Ostrea, Brug. 
The true Oysters have the ligament as just described, and irregu- 
lar inequivalve and lamellated shells. They adhere to rocks, piles, 
and even to each other, by their most convex valve. 
The animal — Peloris, Poll, — is one of tlie most simple of all the 
bivalves, possessing nothing remarkable but a double fringe round 
the mantle, the lobes of which are only united above the head, near 
the hinge ; but there is no vestige of a foot. 
O. edulis, L. The common oyster is well known to every one. 
Its fecundity is as astonishing as its flavoiir is delicious. Among 
the neighbouring species we may observe, 
0.cristata,Vo\\,\\, xx, or the little Mediterranean oyster. 
Among the foreign species we have, 
O. paralitica, L. ; Chemn., VIII, Ixxiv, 681. Round and flat; 
it adheres to the roots of such mangroves and other trees of the 
torrid zone, as the salt-water can reach. 
* See Deshayes, Ann. des Sc. Nat., June, 1825 ; and Ch. Desmoulins, loc. cit. 
Several Hippurites liave been described by La Peyi’ouse under the improper name of 
(jrUioccratitcs. The Cornucopia of Thompson, Journ de Phys. an X, pi. ii, is also 
one of them. 
•b The observations ofM. Deshayes and Audouin even lead us to believe that, in a 
part of these shells, there were two muscular impressions. 
