6. Corbis. One species.
This genus was at first classed by Lamarck with the Lucina; but Cuvier, having discovered that the organization of the animals differed, made this a distinct genus, which was adopted by Lamarck.
Shell transverse, equivalve, no flexuosity; apices curved inward, opposed to each other; two primary and two lateral teeth, the posterior one nearest to the hinge; muscular impression simple, valves sometimes convex, strongly ribbed transversely, striated longitudinally, margins serrated and closely interlocking.
C. fimbriata. The fringed Corbis. Pl. [8], fig. 1.
Species white, rather thick, oval, a little elongated, almost equilateral; the cardinal and the lateral teeth well marked; the muscular impression anterior, rounded.
7. Lucina. Twenty species.
In the hinge and lateral teeth it much resembles the Tellina, but differs from it in never being flexuous. This genus is more easily characterized by the orbicular, compressed, general form of the shell, than by the dental system, which is sometimes entirely effaced.
Shell compressed, regular, orbicular, sub-equilateral; summits small and pointed, inclined anteriorly; hinge similar, but variable; two divergent cardinal teeth, little marked, and sometimes entirely effaced; two remote lateral teeth, with a pit at the base, sometimes obsolete; posterior ligament more or less sunk; two widely-separated muscular impressions, of which the anterior is narrow and long.
Lucina Jamaicensis.
L. Pennsylvanica.