GASTEEOPODA. 331 



tentacular processes ; gills with 2 or more lateral appendages. 

 (A. and H.) 



Distrihutiony Norway (8 species), Britain, Eed Sea. Within 

 tide-marks and in deep water on corallines. The spawn is strap- 

 shaped, and coiled on stones, in July and August. P. ocellata 

 [Plocamophorus, Eiippell) has the cephalic tentacles branched. 



Idalia, Leuckart. 



Etymology, Idalia, Venus, from Mount Idalium, in Cyprus. 



Synonyms, Euplocamus, Phil. PepUdium (Maderse), Lowe. 



Example, I. aspersa, PL XIII., Fig. 6. Coralline zone. 



Animal broadly oblong, nearly smooth, tentacles clavate or 

 linear, with filaments at their base ; head slightly lobed at the 

 sides ; mantle yery small, margined with filaments ; lingual 

 teeth 2.0.2. 



Distribution, 14 species. Norway, Britain (4 species), Medi- 

 terranean, Madeira, Japan. 



Anctjla, Loyen. 



Synoyiym, Miranda, A. and H. 



Type, A. cristata. Alder. 



Animal slender, elongated; mantle entirely adnate, orna- 

 mented with simj)le filaments ; tentacles clavate, laminated ; 

 with filiform appendages at their base ; labial yeil produced on 

 each side. 



Distribution, 2 species. Norway and Britain. Length, -^ inch. 



Ceratosoma. (Gray), A. Adams. 



Etymology, ceratois, horned, soma, body. 



Type, C. cornigerum. Ad. 



Animal oblong, narrow, with two large and prominent horn- 

 like processes on the posterior part of the back, behind the gills; 

 gills 5, bipinnate ; dorsal tentacles clayate, laminated, rising 

 from rounded tubercles, non-retractile ; head with short lateral 

 processes ; foot narrow. 



Distribution, 2 species. Sooloo Sea. (A. Adams.) 



Treyelyana, Kelaart. 1858. 



Body without a cloak. Two dorsal tentacles, without sheaths ; 

 non-retractile. Mouth in front of head, without tentacles- 

 Branchiae in a circular disk on the back, non-retractile. 



Distribution., 1 species (T. Ceylonica). Ceylon. 



