Of the same form as the Psammobia, but differing in the number of teeth,
as the left valve of the Psammotæa has only one tooth; sometimes one
valve is toothless, while the other has two teeth.
Shell transverse oval or oblong; gaping a little at the sides; one
primary tooth on each valve, though sometimes on only one of them;
ligament exterior, attached to callosities at the hinge, and without an
irregular plait.
Psammotæa violacea.
P. zonalis.
P. pellucida.
P. serotina.
P. candida.
P. Tarentina.
P. donacina.
_P. violacea._ The violet Psammotæa. Pl. 7, fig. 5.
Transversely ovate-oblong, sub-ventricose; transversely striated; purple
radiations.
TELLINARIA. Seven genera.
The first five of these genera have one or two lateral teeth, the
remaining two have none.