38 TRACHELIPODA. MUREX. 
provided with a thick cornuous operculum of an oblong 
form, rounded at one end, and pointed at the other. 
Rostellaria lucida. Plate Ill. fig. 29. Found in the 
London Clay at Highgate Hill. 
The sinus close to the pointed canal distinguishes this genus from the genera 
Strombus and Pteroceras ; these having the sinus remote from the. lower 
canal. 
The Rostellarig inhabit the ocean. They are not numerous. 
Fossil species are found in the London Clay, the Greensand, Calcaire- 
grossiér of Paris, and in the Tertiary formations of Bordeaux, and Italy. 
TRIBE V.— CANALIFERA. 
Shell with a more or less lengthened canal at the base of the 
aperture, and of which the right margin does not change its 
form as the animal advances in age. 
SUB-DIVISION I. 
Shell provided with a permanent varix on the outer lip, 
and varices on the spire. 
Genus XXVIII. — TRITON. — Lamarck. 
Generic Character. — Shell ovate or oblong, thick ; with 
interrupted varices, situated at irregular distances, one or 
two on each volution ; spire prominent, and mammillated 
at the apex ; aperture round or oval, terminating above in 
an ascending canal, and below in an elongated and reflected 
beak ; outer lip thickened, reflected, and generally denticu- 
lated within ; whole surface covered with a strong, horny 
epidermis, which is frequently provided with a fringe of 
long ciliated hairs on the outer lip and base of the volutions. 
Operculum thick and horny. 
Triton canaliculatum. Plate V. fig. 27. Found in the 
London Clay at Barton Cliff and Muddiford. 
The rugose inner lip, and the varices never exceeding two on the volutions, 
distinguish the shells of this genus from those of Murez. 
The Tritons inhabit the seas of the East and West Indies, and South Seas. 
The species are but few. Fossil Tritons occur only in the Tertiary formations, 
in the London Clay and Greensand. 
Genus XXIX.—_ MUREX. — Linneus. 
Generic Character,— Shell oblong, subturreted ; spire 
frequently prominent, with an acute apex ; furnished with 
three or more rough, spinous or muricated varices, fre- 
quently digitated, or spinous, or with fringed projecting 
foliations ; aperture suborbicular ; columella smooth; base 
