Distinguished from the Crassatella by the position of the ligament, and
from the Venus by having only two teeth on each valve; one of them on
the left valve projects very slightly.
_C. Danmoniensis._ The Devonshire Crassina. Pl. 6, fig. 1.
Solid, thick, sub-orbicular, sub-equilateral; two very large divergent
teeth on one valve, and two very unequal ones on the other; regular
parallel grooves and ribs; covered with a yellowish epidermis; inside
white; margin broad and plain.
FAMILY IX.
CONCHACEA. Seven genera.
This family is divided into Conchæ fluviatiles, fresh-water shells, and
Conchæ marinæ, sea shells.