Lamarck’s Genera of Shells. 301 
Type. Amphidesma variegata *. 
Shell suborbicular, flattened convex, thin, whitish, inclining 
to purple, with red spots ; nates contiguous, radiated. 16 Spe- 
cies. African Coast? Pl. v. Fig. 37. 
2d Family. 
Corsutea. (2 genera.) 
Shell inequivalve, ligament internal. 
Inequality of the valves is not peculiar to irregular shells ; re- 
gular shells, the individuals of a species of which are perfectly 
alike, are often inequivalve, as the cardia, and others, and also 
those of the present family, which are regular, inequivalve, 
inequilateral, and transverse. They are sea shells, and generally 
small, or of moderate size, not sensibly gaping, and one of 
the beaks is always more prominent than the other. 
1. Corbula t. 
Shell regular, inequivalve, inequilateral ; not at all, or very 
slightly, gaping. One conical, curved, ascending tooth on each 
valve, and, beside it, a pit. No lateral teeth. Ligament 
internal, fixed in the pits. 
The corbulee are distinguished from the ungulinee and crassa- 
tellze, by the inequality of their valves, and by the strong, pro- 
minent cardinal tooth, which characterizes them. 
Type. Corbula nucleust. (Mya inequivalvis. Montag.) 
Shell globoso-triangular, transversely striated, somewhat 
wrinkled ; one of the nates more gibbous than the other. New 
Holland. 13 Species. Pl. v. Fig. 38. 
2. Pandora §. 
Shell regular, inequivalve, inequilateral, transversely oblong ; 
upper valve flattened, lower convex. Two oblong, diverging, 
unequal cardinal teeth in the upper valve; two oblong pits in 
the lower. Ligament internal. 
The pandore are distinguished from the placune, by having 
* Variegated. + A little basket. 
t A kernel. Wamarck’s sixth species—his type is C. australis. 
§ From say and wes, every gift. A personage of fabulous history, on 
whom all the heathen gods bestowed a gift. 
’ 
