MOLLUSCA, 153 
The foot extends on each side beyond the body. From the 
manner in which the blood is aérated, the auricle and ven- 
tricle are placed longitudinally, the latter being anterior. 
Genus Oncurprum.—Cloak tuberculated. Snout en- 
larged and emarginate. Tentacula two in number, with 
eyes at the tips. This genus was instituted by Dr. Buchan- 
an, (now Hamilton), in Lin. Trans., vol. v. p. 132, for the 
reception of a species which he found in Bengal, on the 
leaves of Typha Elephantina. It is not, according to this 
naturalist, “like many others of the worm kind, an herma~ 
phrodite animal ; for the male and female organs of genera- 
tion are in distinct individuals. I have not yet perceived 
any mark to distinguish the sexes, while they are not in 
copulation; as, in both, the anusand sexual organs are placed 
in a perforation, (cloaca’communis), in the under part of the 
tail, immediately behind the foot; but, during coition, the 
distinction of sexes is very evident, the penis protruding to 
a great length, considering the size of the animal.” 
2d Subdivision. 
Cloak and foot not parallel; the viscera contained in a 
spiral, dorsal protuberance, protected by a shell. 
This group includes the animals usually denominated 
Snaits. They bear a very close resemblance to the slugs. 
The shield, however, has a thickened margin in front, des- 
tined to secrete the matter of the shell. In the part corres- 
ponding with the centre of the shield in the slugs, there is, 
(as Cuvier has characteristically termed it), a natural rup- 
ture, through which the viscera are protruded into a conical 
bag twisted spirally. In this bag are contained the principal 
viscera, the liver occupying its extremity. The body of the 
animal is attached to the pillar of the shell by a complicated 
muscle, which shifts its place with the growth of the animal. 
