224 Scientific Proceedings, Royal Dublin Society. 



100 miles west of Co. Donegal. Pneumodermopsis Michaelsarsi, Bonnevie, 

 occurred further west, being met with off the Porcupine Bank, about 200 

 miles west of Co. Galway, over soundings of 860 fathoms. All the species 

 enumerated by Bonnevie among the Gymnosomata, taken by the " Michael 

 Sars " North Atlantic Deep Sea Expedition of 1910, are represented here 

 except Pneumoderma atlantica, Bonnevie ; Fowlerina Hjortii, Bonnevie ; 

 Microdonta longicollis, Bonnevie ; and Glione limacina, Phipps. The last- 

 named has been purposely omitted, having previously (Massy, 1909) been 

 shown to be very abundant in the area. The fact that Bonnevie got no 

 specimens of Vnewmodermopsis paucidens seems to suggest that, although 

 originally described from a specimen taken on a voyage from Brazil, this 

 species may have its headquarters in the Atlantic off the south-west coast of 

 Ireland. 



All the specimens were examined and measured after preservation in 

 5 per cent, formalin. In the records which follow, the localities are indicated 

 by station numbers, of which particulars are given at pp. 241, 242. 



List of Gymnosomatous Pteropods taken in British and Irish Waters. 



Pneumodervwpsis ciliata (Ggbr.). 



„ patocidens (Boas). 



„ Michaelsarsi, Bonn. 



„ macrochira, Meis. 



„ oligocotyla, sp. n. 



Spongeobranchaea polycotyla, sp. n. 

 Glionopsis longicirrata, sp. n. 

 Glione limacina, Phipps. 



„ gracilis, Massy. 

 Gephalobrachia macrochaeta, Bonn. 



„ Bonnevii, sp. n. 



Notobranchaea tetrabranchiata, Bonn. 

 Thliptodon atlanticus, sp. n. 

 ,, rotundatus, sp. n. 



Pelseneer (1887, p. 10) drew up a key of the seven genera of Gymnoso- 

 matous Pteropods known in his day, basing his system on the gills. Bonnevie 

 (1913, p. 62) has shown what inconsistent organs these are; and in his table 

 (loc. cit., pp. 60-61] the median tooth of the radula is regarded as the most 

 important character. Partly owing to the incomplete condition of some of 

 the new species here described, which necessitated a somewhat provisional 

 classification, and also on account of the paucity of our knowledge of this 



