NORWEGIAN OPISTHOBRANCHIATE MOLLUSCA 9 



Externally the present species differs from T. homhergi 

 and approaches T. plebeia in the position of the anus, which 

 appears far in front of the middle of the right side.^ 



Grieg hesitated in establishing this form as a new species, 

 and considered it to be only a giant variety of T. plebeia (1897) or 

 a T. homhergi (1913), but with respect to the differences held forth 

 above and which seem to be constant, above all with respect to the 

 raandibulae, which organs may certainly be suitable for basing a 

 subdivision of the genus, I cannot share Grjeg's view, but consider 

 it necessary to attribute a specific account to the present form. 



Remarks on Fam. Tritoniidae. 



On account of the compact liver mass of Tritoniidae, these 

 are included by Eliot (1910)^ in the tribe Holohepatica, while, 

 on the contrary, Pelseneer (1906)^ has established a special tribe, 

 Tritoniomorpha, to comprise this and a few other families (for 

 instance Dendronotidae, Tethyidae). Bergh, in his classification 

 of the Nudibranchia"^ maintains, on the other hand, their position 

 among the Cladohepatica. In reality the Tritoniidae have their 

 closest relationship to this latter group, though they recall the 

 former in the undivided shape of their liver. This, however, 

 shows two different dispositions, in Tritonia only one single 

 liver mass with a single duct exists; in Marionia, however, 

 there is a main posterior liver and a small anterior lobe on the 

 right side with its own efferent duct. In all other Cladohepatica 

 there is a large posterior liver canal leading from the chief part 

 of the liver, and some ones, or at least one on the right side. 



1 Like the specimens mentioned by Grieg the present one had in its 



stomach a large quantity of still undigested parts of a Paramuricea 



stock. 

 ^ Alder & Hancock, Monograph of British Nudibranchiate Mollusca, Part 



VIII (Supplementary). 

 3 Ray Lankester, A Treatise on Zoology. Part. V. Mollusca. London. 

 '' System der nudibranchiaten Gasteropden. Sempers Reisen im Archipel 



der Philippinen. T. II. H. XVIII. Wiesbaden 1892. 



