108 MOLLUSCA. 
with a tooth. The Turbo interstincta, unidentata, plicata, 
Sandivicensis and insculpta of Montagu, are of this genus. 
They have no resemblance in their structure to the Lin- 
nzean volute ; although they have been inconsiderately as- 
sociated with them by the authors of the Descriptive Cata- 
logue. The preceding genera are formed of marine shells ; 
those that follow live on the land. 
In the genus CycLostoma, the mouth is circular, with 
united, and often reflected margins. The animal is furnish- 
ed with an operculum. The 7. elegans of Montagu is the 
only British species of the genus. 
The species which are related to the Turbo bidens per- 
versus and muscorum of Linnzeus, constitute a very natural 
family, which may be termed Pupacea, distinguished by 
the mouth being furnished with teeth or testaceous lami- 
nee, and the last whorl nearly the same or less than the pre- 
ceding. Perhaps the most convenient way of dividing them 
is into two sections, the first including the dextral, and the 
second the sinistral shells. 
The dextral pupacea form two genera. The Pupa, as 
originally constructed by Lamark, was equally faulty with 
many of the old Linnean genera. As it has been restrict- 
ed to include dextral shells, with the animal possessing four 
tentacula, with eyes at the tips of the two longest, it can 
embrace the muscorum, sexdentatus, tridens, and junipert 
of Montagu. In the genus CAarycurum, formed by Miil- 
ler, the tentacula are only two in number, with the eyes 
placed at the base. It is represented by the 7. carychium 
of Montagu. 
The sinistral pupacea form likewise two genera. The 
first, which is the Clausilia of Draparnaud, contains sinistral 
shells, with the animal furnished with four tentacula, with 
