RIIODOTE. 



Species of Acteonia. 

 corrugate, Alder and Banc. sinistra, Quatref. 



Genus CENIA, Alder and Hancock. 



Body with a slight ridge on each side ; hack elevated. 

 Head sub-angulated, with two linear, dorsal tentacles, he- 

 hind and exterior to which are the eyes. 



Syn. Ictis, Alder and Hancock, not Kaup. 



Ex. C. Cocksii, Alder and Hancock, pi. 68, fig. 1. 



The animals of this genus inhabit pools between tide- 

 marks ; the tentacles are obtuse and cylindrical. 



Genus FUCICOLA, Quoy and Gaimard. 



Body limaciform, simple, without lateral lobes or seini- 

 cireular expansions. Tentacles two, simple, club-shaped. 



Syn. Dermatobranchus, Van Hass. Abranchus, Van 

 Has,. Fucola, Quoy and Gaim. (error typ.). 



Ex. F. rufa, Quoy and Gaimard, pi. 68, fig. 2. 



This genus, remarkable for its simplicity of organization, 

 is pelagic in its habits, living on floating sea- weed. 



Genus RHODOPE, Kollikcr. 



Body creeping, vermiform, convex above, flat beneath, 

 without mantle, without shell, without gills, without tentacles 

 or any appendages. 



Ex. R. Veranii, Kolliker. 



This curious genus, characterised principally by its nega- 

 tive peculiarities, was observed by its author on algfiB, at 



