192 MANUAL OF THE MOLLUSC A. 



Animal oblong or elongated ; tentacles laminated, non-retractile, sheath- 

 less ; head-veil bordered with tubercles or tentacular processes ; gills with 2 

 or more lateral appendages. (A. and H.) 



Bistr. Norway, 5 sp. Brit. Red 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, Riippell) has the cephalic 

 tentacles branched. 



Idalia, Leuckart. 

 Etym. Idalia, Venus, from Mt. Idalium in Cyprus. 

 Si/ii. Euplocamus, Phil. Peplidium (IMaderEc) Lowe. 

 • Ex. I. aspersa, PI. 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 very smaD, 

 margined with filaments; lingual teeth 2.0.2. 

 Distr. Norway, Brit. (4 sp.) Medit. Madeira. 



Ancula, Loven. 



Syn. Miranda, A. and H. Type, A. cristata. Alder. 



Animal slender, elongated; mantle entirely adnate, ornamented with 

 simple filaments ; tentacles clavate, laminated ; with filiform appendages at 

 their base ; labial veil produced on each side. 



Distr. Norway, Brit. Lon. \ inch. 



Ceratosoma (Gray), A. Adams. 



Etym. Ceratois, horned, soma, body. Type, C. cornigerum. Ad. 



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

 cesses on the posterior part of the back, behind the gills ; gills 5, bipinnate ; 

 dorsal tentacles clavate, laminated, rising from rounded tubercles, non- 

 retractile ; head with short lateral processes : foot narrow. 



Distr. Sooloo sea. (A. Adams.) 



FAMILY YII. Tritoniad.e. 



Animal with laminated, plumose, or papillose gills, arranged along the 

 sides of the back ; tentacles retractile into sheaths ; lingual membrane with 

 1 central and numerous lateral teeth ; orifices on the right side. 



Tritonia, Cuvier. 



Ex. T. plebeia, PI. XIII. fig. 7. 



Animal elongated ; tentacles with branched filaments ; veil tuberculated 

 or digitated ; gills in single series on a ridge down each side of the back ; 

 mouth armed with horny jaws; stomach simple; liver compact. 



Distr. Norway, Brit. Under stones at low-water, — ~5 fm. F. Hom- 

 bergii, Cuv. found on the scallop-banks, attains a length exceeding G inches. 



