MOLLUSCA: 10l 
As originally constituted, the genus of Linnzeus contain- 
ed species of very different characters, so that many new 
genera have been formed. ‘To Bruguiére, Lamark, and Dra- 
parnaud, we owe all the improvements which have taken 
place. 
The modern genus Buta includes those shells which cor- 
respond with the following character :—“ Testa univalvis, 
convoluta, ovato-gibbosa vel cylindracea: spira non exserta, 
apertura longitudine testa, labro acuto.” The B. ampulla 
is the type of the genus. 
The genus OvuLa, instituted by Bruguiére, is more nearly 
related to the cyprea than to the bulla. It differs, however, 
from the former, in the left margin of the lip being smooth ; 
and from the latter, in the edges of the mouth being rolled 
inwards, and in the shell being produced at both ends. The 
B. ovum of Linnzeus is the type of the genus; the B. patula 
of Pennant. 
— The bulla terebellum has been employed by Lamark to 
constitute his genus TEREBELLUM. The canal at the base 
of the mouth, and the truncated pillar, furnish the generic 
characters. 
Linnzeus was for some time uncertain where to place those 
shells which he at last inserted in the genus bulla, under the 
trivial names ficus and rapa. These, with afew of the mu- 
rices of the same author, constitute the genus PyruLa of 
Lamark. Its canaliculated base removes it from the bulla, 
while the short spire, the swelling of the last whorl, the 
smooth pillar, and pyriform shape, distinguish it from all 
those with which it is apt to be confounded. It is more 
nearly allied to the Fusus than to any other. 
The preceding genera consist of species which live in the 
sea. The B. virginea is a terrestrial shell, and ought to 
