832 Proceedings of the Royal Irish Academy. 



XII. E.EPOET 0^' THE OPISTHOBEAKCHIATE MoLLITSCA. By W. I. 



Beaumont, b.a. 



Introduction. 



At the request of my colleagues I tave prepared the following Report 

 on the Opisthobranchiate IToUusca observed at Valencia. It is due 

 to Mr. Gamble, who had gained some knowledge of this group at 

 Plymouth previous to our first visit to Yalencia, to state that the 

 determination of species was to a large extent carried out by him. For 

 the most part, however, specimens were examined by myself also ; in 

 the few cases where he is solely responsible for the determination, 

 notice is made of the fact. 



Altogether 48 species^ of Nudibranchs, and 8 of Tectibranchs, were 

 foujid ; of which all but two of the former and one of the latter occur 

 in Yalencia Harbour itself — a very fair proportion of the British 

 shallow-water species. Better opportunities for work outside the 

 harbour would, no doubt, have added a number of the deeper-water 

 forms to our list ; from "which, for example, so common and widely 

 distributed a genus as Tritonia is absent. 



Our most interesting finds were : — JEoUs ( Cuthona) PeacMi (a 

 species lost sight of, apparently, since the time of Alder and Han- 

 cock) ; a large specimen of Lomanotus (the third found in Britain so far 

 as I know, and serving to throw some light on the species of that 

 genus) ; a specimen of a small Doris (previously taken in the Irish 

 Sea by one of us, and believed to be an undescribed species) ; and one 

 example of the rare Idalia LeaeMi. 



Another feature of interest was the extraordinary abundance of 

 certain Solids ( Cavolina aurantiaca, Coryphella lineata, Facelina Prum- 

 mondi, F. coronata) and of Bendronotiis arlorescens, on the bottoms of 

 two hulks which were beached after lying at moorings in the harbour 

 for a year or more. Here they had been feeding on the numerous 

 colonies of Tubularia larynx, and many individuals were of exceptional 

 size. Some of these species were not found by us elsewhere. 



It has not been thought necessary to enter into the synonymy or 

 distribution except in a few cases. The classification and nomencla- 

 ture of Bergh (1892, System der Kudibranchiaten Gasteropoden) have 

 been followed, for the most part, in the arrangement of the Nudibran- 

 chiata (all references to Bergh are to that work). In the case of each 



1 Inclusive of 5 species of Ascoglossa. 



