NORWEGIAN OPISTHOBRANCHIATE MOLLUSCA 19 



a prostata does not occur and where the female and the male 

 genital openings are, contrary to the real Pleurohranchaea, 

 separated. Goniaeolis may however be referred to a stage some- 

 what less differentiated than Oscaniopsis and Pleurohranchaea, a 

 fact which appears in the beginning development of a recepta- 

 culum seminis, and in a rather incomplete differentiation of the 

 mucus gland and the albuminiparous gland as well as of the 

 part of the oviduct bearing them. On the other hand Goniaeolis 

 is more specialized in the separate genital openings and the 

 rudimentary division of the vagina. 



Another primitive character is shown in the liver, which 

 does not enter the dorsal papillae, but still forms a compact 

 mass, consisting of a large central lobe and some smaller ones 

 on each side, debouching with their own ducts into the stomach. 

 The hver is, in addition, completely separated from the her- 

 maphrodite gland. To the significance of this condition and its 

 account of the affinities we will return later on. 



Also in the external habitus of this animal we find remains 

 of an origin from more primitive forms of Opisthobranchia. 

 Already when describing this species under the name G. lohata 

 I was in much doubt, how to interprète the cutaneous lobes of 

 the right side and their presence on this side only. The occurrence 

 of veins on the under side of the posterior lobe made me think 

 of a metamorphosed ctenidium, but the general structure and 

 the presence of an anterior lobe were against such an explanation. 



The lobes in question are probably the remnant of a pro- 

 jecting eave of the notum, the left margin of which had already 

 early been completely reduced, so that only the right margin 

 persisted. Rather this state of affairs is met with in Pleuro- 

 hranchaea, where the notum is not sharply defined on the left 

 side but overhanging on the right and produced into a short 

 siphon behind [PI. meckelii). In P. maculata figured by Quoy & 

 Gaimard (cf. also Pilsbry Man. of Conch. 16, 1896, pi. 53, fig. 89) 

 the siphon is replaced by a flattened lappet behind the anus. 



