178 THE GASTROPODA 



rhinophores very long, non-retractile ; British. Ancula, Loven ; mantle 

 border scarcely distinguishable, without appendages ; rhinophores branched ; 

 British (Fig. 163). Doridunculus, Sars. Lamellodoris, Alder and Han- 

 cock. Ancylodoris, Dybowsky, the only freshwater Nudibrunch, from Lake 

 Baikal, probably belongs to this family. FAMILY 3. HETERODORIDIDAE, 

 Fischer. No branchia. Genus Heterodoris, Verrill and Emerton. 

 FAMILY 4. DORIDIDAE, Gray. Mantle oval, covering the head and the 

 greater part of the body ; anterior tentacles ill developed ; branchiae 

 generally retractile. Genera Hexabranchus, Ehrenberg ; branchiae made 

 up of separate fascicles, retractile within distinct 

 cavities. Doris, Linnaeus ; mantle elliptical, 

 covering the whole body ; branchiae tri- or 

 quadri-pennatifid ; British (Fig. 160, C). (Sub- 

 genera Archidoris, Bergh. Rostanya, Bergh. 

 Aldisa, Bergh. Cadlina, Bergh. Jbrumio, Bergh. 

 Platydoris, Bergh). Chromodoris, Alder and 

 Hancock ; body long and narrow ; foot longer 

 than the mantle ; branchial plumes simply 

 pinnate. FAMILY 5. DORIDOPSIDAE, Alder. 

 Pharynx suctorial ; no radula ; peri -branchial 

 rosette on the dorsal surface, above the mantle 

 border. Genus Doridopn*, Alder and Hancock. 

 FAMILY 6. CORAMBIDAE, Bergh. Anus and 

 branchia posterior below the mantle border. 



Genus-6'orrofc, Bergh (Fig. 164). FAMILY 7. 

 g, paiiial gills : m, mouth ; ]>a, PnYLLiDiiDAE, Alder and Hancock. Pharynx 

 H.'Fischer!/' to * suctorial ; branchiae surrounding the body and 



placed between the mantle and the foot. Genera 



Pkyllidea, Cuvier ; anus dorsal. Fryeria, Gray ; anus posterior between 

 the mantle and the foot. 



The three last families constitute the sub -tribe " Porostomata," 

 characterised by the reduction of the buccal bulb, which is transformed 

 into a suctorial apparatus. 



TRIBE 3. EOLIDOMORPHA ( = Cladohepatica). 



Nudibranchs in which the whole of the liver is contained in the 

 integuments and the tegumentary papillae (Fig. 77). The genital duct 

 is diaulic, and the male and female orifices are contiguous. A pair of 

 laterally placed mandibles is present (Fig. 73, A). The anus is antero- 

 lateral, except in the Proctonotidae, in which it is median. The tegu- 

 mentary papillae are not ramified : they frequently contain terminal sacs 

 (cnidosacs), which communicate on the one hand with the exterior, on the 

 other hand with the digestive canal (Fig. 165). The cnidosacs contain 

 neinatocysts, which according to Wright and to Grosvenor are derived 

 from the various species of Hydroids on which the animals feed. The 

 nematocysts are invaginated while they are in the cnidosacs, but when 

 expelled from them they are evaginated (Fig. 166). In some species of 

 Hedyle and Pseudovermis, in which there are no tegumentary papillae, 



