TRITONIIDAE. 3 



Galvinella antarctica has eyes of normal size, and Notaeolidia depressa (like 

 N. gigas) very minute ones. In the other specimens no eyes could be found, and 

 though their absence cannot be regarded as certain, it is probable that the larger 

 animals, at any rate, have none. As preserved, the specimens are mostly yellow, but it 

 would appear that when alive they were milk-white or colourless. The Nudibranchs of 

 the Scottish National Antarctic Expedition seem to have been white or pinkish. 



TRITONIIDAE. 



THIS family consists of large slug-like animals of a somewhat rectangular shape. They 

 have an undivided liver, no blood gland, one spermatotheca, a frontal veil, strong jaws 

 and a large radula with a central tooth. As a rule they have arborescent branchiae set 

 on the dorsal margin, simple rhinophores surrounded by plumes and retractile into 

 raised sheaths, the hermaphrodite gland spread over the liver, and numerous smooth 

 hamate lateral teeth, of which the first is larger than the others. 

 Five genera seem referable to the family : 



1. Tritonia Cuvier has all the typical characters mentioned above, and simple 

 projections on the frontal veil. Candiella Gray is a subgenus. 



2. Marionia Vayssiere differs from the other known genera in having the stomach 

 armed with horny plates. Otherwise it resembles Tritonia, but the processes on the 

 frontal veil are generally branched. 



3. Atthila Bergh has papillae on the back, perfoliated rhinophores, a smooth frontal 

 veil, teeth partly denticulate, and a different arrangement of the hermaphrodite gland. 



4. Tritoniopsis Eliot (Trans. Roy. Soc. Edin., 1905, vol. XLI., part III., p. 530) 

 has ridges on the back and a divergent radula. 



5. Tritoniella gen. nov. resembles Tritonia in most points, but differs from it and 

 from all the known genera in having not arborescent branchiae but simple processes or 

 crenulations of the mantle margin somewhat like those of Lomanotus. The back 

 bears ridges. 



Heterodoris Verrill, from New England, very possibly belongs to the same family, 

 and I cannot help suspecting that it is allied to Tritoniella, but the description is 

 defective in some important points, and it is impossible to say to what group of the 

 Nudibranchiata the animal should be referred. 



Marionia is common in the tropics, the furthest points from which it is recorded 

 being the Mediterranean and Buenos Ayres, but the other genera seem to prefer the 

 colder seas. 



TRITONIA (Guv.). 



TWENTY-SIX species of this genus are registered (see Eliot, Jour. Mar. Biol. Assoc., VII. 

 (1906), p. 335), but some of them should probably be referred to Marionia, as the 

 difference between the genera is anatomical and the descriptions often imperfect. 



