104 MOLLUSCA. 
sufficiently obvious characters of distinction. The V. can- 
cellata of Linnzus is the type of the genus. 
In the genus TurBINELLUS the shell is turbinated, sub- 
fusiform, and canaliculated at the base, having from three 
to five transverse compressed plicz on the pillar. The V. 
pyrum is the type of the genus. 
23. Buccinum.—This is another of the Linnzan genera 
of shells, which has undergone great alterations. As origi- 
nally constructed, it embraced many distinct groups of shells, 
which Bruguiére and Lamark have since formed into ge- 
nera. The restricted character of the genus Buccinum is 
thus defined by the last mentioned author : “ Testa unival- 
vis, ovata vel elongata. Apertura oblonga, basi emargina- 
ta, nudata, canali nullo. Collumella convexa plana.” 
Bruguiére separated the genus Cassis, in which the 
opening is oblong and denticulated on the right side, with 
a short canal towards the back of the shell. The right 
margin has a callous border. The Buceinum cornutum of 
Linneeus is the type of the species. 
The genus TEREBRA was likewise formed by the same 
author. It is remarkable for its turreted form, the spire 
being at least twice as long as the mouth, and the pillar at 
the base twisted. ; 
In the genus Nassa the groove in which the mouth ter- 
minates is reflected as in Cassis, but the left edge of the 
mouth is callous, and forms upon the pillar a transverse fold. 
The Purpura is readily distinguished from the Buccinum 
and Murex, with which it has often been associated by its 
naked compressed pillar, ending in a point at the base. 
The genus Dottum is distinguished by its bellied forms 
and transverse rings, together with the margin on the right 
side being denticulated its whole length. 
