ORDER PECTINIBRANCHIATA. qi 
Montfort particularly designates, by the name OVUL&, 
those in which the external margin is transversely wrinkled, 
(Bulla ovum, L.) 
Those in which the two extremities of the aperture are 
prolonged into a canal, and in which the external margin is 
not wrinkled, he denominates VOLV&. (Bulla volva, L.) 
When this external margin is not wrinkled, nor the extre- 
mities of the aperture prolonged, he styles them CALPURNE. 
(Bulla verrucosa, L.) 
TEREBELLUM, Lam. 
An oblong shell, with a narrowed aperture, without folds or 
wrinkles, and increasing regularly in width to the end opposite 
to the spire, which is more or less salient, according to the 
species. The animal is not known. (Zerebellum subulatum, 
Lam., &c.) 
VoLuTA, Lin., 
Varies as to the form of the shell and that of the aperture, but 
is recognized by the emargination, without a canal, which 
terminates it, and by the salient and oblique folds of the colu- 
mella. From this genus Bruguiéres first separated 
OLIvA, Brug., 
So named from the oblong or elliptical shape of the shell, the 
aperture of which is narrowed, long, and emarginated oppo- 
site to the spire, which is short; the folds of the columella are 
numerous, and resemble strize; the whorls are sulciform. 
These shells are quite as beautiful. as the cyprea. (Oliv. 
subulata, Lam., &c.) 
The animal has a large foot, the anterior part of which 
(before the head), is separated by an incision on each side ; 
its tentacula are slender, and bear the eyes on their sides, 
about the middle of their length; the proboscis, siphon, and 
