ROSTELLARIA. TRACHELIPODA. 37 
The position of the sinus, near the extremity of the outer lip, and it also 
being digitated, together with the short spire, distinguish the shells of this 
genus from those of Rostel/aria ; and the lobes and curved canal separate them 
from the Strombi. 
There are but few species of Péeroceras, and these inhabit the tropical seas. 
The fossil species are rare, and are met with in the rocks of the Oolitic 
group. 
Genus XXV.— APORRHAIS. — Petiver. 
Generic Character. — Shell turreted, fusiform ; aperture 
subquadrate, ending above ina canaliculate groove, and be- 
low in a slightly twisted beak, which is canaliculate within ; 
the outer lip expanded, and its margin provided with digi- 
tated lobes ; inner lip broad, with a thick coating of enamel, 
extending the whole length of the body. 
Aporrhais calcarata. Plate IV. fig. 37, Found in the 
Whetstone pits at Blackdown ; the fossil species are only 
known in the newer formations. 
The shells of this genus inhabit the ocean, and are principally European, as 
none are known to exist south of the Mediterranean, 
Genus XXVI. — HIPPOCHRENES. — Montfort. 
Generic Character.— Shell oblong-ovate; body large ; 
spire of medium length, smooth and taper ; aperture long, 
narrow, ending ina straitened canal, both above and below ; 
outer lip large, and much expanded, and but slightly re- 
flected; columella provided with a thick glazing, which 
usually extends high upon the spire, sometimes beyond 
its tip. 
Hippochrenes macropiera. Plate III. fig. 24. Found in 
the London Clay at Hordwell and Highgate Hill. 
The shells of this genus are marine, and only occur in a fossil state. 
Genus XX VII.— ROSTELLARIA. — Lamarck. 
Generic Character. — Shell turreted, or fusiform ; spire 
uniformly longer than the aperture ; the superior volutions 
generally longitudinally grooved, aperture oblong, its upper 
parts prolonged into an elongated narrow canal, which, in 
some instances, extends to the apex of the spire, and not 
unfrequently turns down on the opposite side ; base with a 
more or less lengthened canal, pointed beneath ; outer lip 
in the infant state, thin, but becomes greatly dilated with 
age, entire, or dentated at its lower margin, or digitated ; 
outside covered with a thin, horny epidermis ; aperture 
