T. carinifera.
T. Australis.
T. Virginiana.
T. bicingulata. The twice-girdled Turritella. Pl. [24], fig. 5.
Species that answers to the above description.
T. terebra. The auger Turritella.
Taper, pointed, acute transverse striæ, the intermediate spaces prominent and acute; white, reddish, or cream coloured.
FAMILY XVI.
Canalifera. Eleven genera.
1. Cerithium. Thirty-six species.
A beautiful and numerous genus of turreted shells, with an expanded outer lip and short beak; the greater part are marine; many are found at the mouths of rivers, and a few in lakes, though none can properly be called river shells. In appearance they are like an elongated pyramidal cone, and the spire is at least two thirds the length of the shell. The exterior is seldom smooth, but striated, tuberculated, granulated, or spinous.