oxciiidium. 233 



like, entirely covering the back ; respiratory orifice pos- 

 terior, at the right side, under the margin of the mantle. 

 Foot narrow, elongate, simple posteriorly. Vent separate 

 from the respiratory orifice, posterior. Sexes united ; male 

 organ under right tentacle, female orifice at posterior ex- 

 tremity of body. 



Shell none. 



Mr. Albany Hancock has ascertained that the heart in 

 Peronia Celtica, a British species, is placed in front 

 of the lung, whereas in other Pulmonifera it is situated 

 behind the respiratory organ. The vent, moreover, is dis- 

 tinct from the breathing orifice, which is not the case in the 

 Heliciche and Arionida. The animals of this group seem 

 to approach in their habits those of the Ellobiida, living 

 in damp situations near fresh water, or in the immediate 

 vicinity of the sea. From the nature of their lingual 

 armature they are probably herbivorous, feeding on the 

 dead and decaying leaves and wood of tropical countries. 



Genus ONCHIDIUM, Buchanan. 



Eye-peduncles club-shaped ; oral appendages lobate, 

 simple, undivided. Mantle coriaceous, convex, tubercular. 



Syn. Oncidium, Agassiz. Onchidia, Swains. ? Oris, 

 Iiisso. 



Ex. 0. Typhse, Buchanan, pi. 81, fig. 1, 1, a. 



The type of this genus inhabits Bengal, where it is found 

 on the leaves of the Typha elejphantina. Many undis- 

 covered species doubtless exist in equatorial regions in the 

 damp forests and among decaying leaves and rotting fungi, 

 but perhaps have been overlooked or confounded with the 

 Li ma as. 



