MOLLUSCA. 455 



the pulmonary cavity is situate on the right side posteriorly, 

 under the shell. A little in advance of this, is another 

 opening, in the middle of which is the funnel-shaped aper- 

 ture of the anus. The sexual organs are united, and placed 

 at the base of the right tentaculum. 



It is not improbable, according to Fkrrussac, that the 

 Limax nudus cinereus terrestris of Sloane, Jam. ii. p. 190, 

 Tab. 233, f. 2, 3, may belong to this genus, or rather, that 

 the individual brought home by Sloane, may have been 

 the identical specimen submitted to M- Blainville's exa- 

 mination. 



19. Onchidium Cloak tuberculated. Snout enlarged 



and emarginate. Tentacula two in number, with eyes at 

 the tips. 



This genus was instituted by Dr Buchanan (now Hamil- 

 ton), in Lin. Trans, vol. v. p. 132, for the reception of a 

 species which he found in Bengal, on the leaves of Typha 

 Elephant'ina. It is not, according to this naturalist, " like 

 many others of the worm kind, an hermaphrodite animal; for 

 the male and female organs of generation are in distinct indi- 

 viduals. I have not yet perceived any mark to distinguish the 

 sexes, while they are not in copulation; as, in both, the anus 

 and sexual organs are placed in a perforation (cloaca commu- 

 nis), 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 

 Snails. They bear a very close resemblance to the Slugs. 

 The shield, however, has a thickened margin in front, 

 destined to secrete the matter of the shell. In the part coiv- 



