This genus is easily distinguished from all screwlike shells by a sinus
on the right margin of the aperture, not existing in any other shell of
similar form.
Shell marine, turreted, not pearly, rather thin, striated according to
the turning of the spire, which is very pointed, and has numerous
whorls; aperture rounded; the edges disunited posteriorly; the right
extremity thin, and, when perfect, having a light sinus about the
middle; operculum horny.
Turritella duplicata.
T. terebra.
T. imbricata.
T. replicata.
T. fuscata.
T. cornea.
T. brevialis.
T. bicingulata.
T. trisulcata.
T. exoleta.
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.