GENUS BUCCINUM. 99 
surrounds the suture, and the other only borders the circum- 
ference. Epidermis thick and brown. 
Length 6 lines. Width 43 lines. 
( 
Inhabits the Mediterranean, upon the coasts of France, of 
Corsica, and of Sicily ; the Adriatic, and the Ocean, towards 
the gulf of Gascony. 
Risso, in his work on the South of Europe, has described two 
specimens of this species under the names of Cyctopr Dono- 
viana and Cycuore pellucidus, p. 271, No. 718 and 719. These 
appear to be only worn and discolored specimens. 
The principle too often followed for the establishment of 
groups among shells, has given rise to many errors; these 
groups, arranged by an examination of the superficial charac- 
ters of shells, comprise a great number of dissimilar species, be- 
longing even to other genera; and species are rejected as dis- 
tinct, which ought to be united. These characters, such as the 
color, the folds, the striz, the whirls, run into each other in a 
manner so insensible, or differ so completely, that it is impossi- 
ble by them to point out the limits between species. 
Thus, in the genus Buccrnum, which we have just been de- 
scribing, we see numerous specimens, obviously varying in the 
longitudinal folds, tubercles, and transverse strie#, which are 
found upon their surface ; in some, these folds, at first very prom- 
inent, disappear, and sometimes leave tubercles which shew the 
vestige of them; in others the strie are less distinguished. 
Sometimes the whirls are strongly canaliculated, whilst upon 
other shells of the same species, the suture is scarcely apparent. 
These variations depend upon differences of sex, of age, or of 
locality. But the same species invariably presents two charac- 
ters which are constant, or at least subject to less variation, that 
of the general form, and the aperture of the shell, which, I think, 
