MOLLUSCA: re 
subnullis.” To this genus Lamark brings the Tellina lactea 
and divaricata of Linnzeus, and the muricata of Chemn. 
(Conch. vol. xi. p. 209, tab. 199, fig. 1945-6), together with 
the Venus fimbriata, and Pensylvanica of Linnzus, and the 
Jamaicensis of Chemn. (Conch. vol. vii. p. 24, tab. 39, fig. 
408-9). Cuvier, however, has restored the T.lactea to the 
genus Loripes, which Poli instituted for its reception. 
7. Carprum.—This is, perhaps, the best constructed 
genus which Linneus formed. The characters are definite 
and obvious, and all the species are naturally allied. Hence 
few changes have taken place in their arrangement. The 
animal constitutes a new genus in the system of Poli, which 
he terms cerastis. 
Cuvier is disposed to constitute a new genus under the 
title Hemicarpra, for the reception of the C. cardissa ot 
Chemn., commonly called the Venus-heart cockle. The 
truncated appearance on the one side, and its being carin- 
ated in the middle, point out a conformation of the inhabi- 
tant different fromi the true cockles. Of this new genus we 
possess some fossil species. 
8. Macrra.—The ligament, in the marine bivalves, is, 
in general, placed on the outside, but in this genus, of which 
Lamark has formed his family mactreacea, the ligament 
is internal, and inserted in a cavity at the hinge formed for 
its reception. This family, as it stands at present, contains 
several well characterised genera. 
In the restricted genus, MAacrra, as represented by the 
M. stultorum of Linnzus ; the shell gapes a little, and the 
lateral teeth are strong, and lock into each other. The 
shells with age arrive at a considerable thickness. The in- 
habitant belongs to the genus callista in the system of Poli. 
The genus CrAssaTELLA of Lamark contains shells which 
