333 



PTEROSOMA, Lesson, CLAIMED AS A HETEROPOD. 



By C. Hedlet, F.L.S., etc. 



(By permission of the Trustees of the Australian Museum, Sydney.) 



Read June 14<A, 1895. 



"While collecting on March 17th of this year the jelly-like and trans- 

 parent oceanic animals Abyla, Bassia, Calpe, and Biphyopsis, among 

 the Siphonophorse, the Amphipod Oxycephalus, and the Pteropod 

 Cavolinia, cast ashore by an easterly gale at Mavonbra Bay, near 

 Sydney, my colleague, Mr. T. AVhitelegge, detected a molluscan 

 \isitor to which several years' scrutiny of the pelagic fauna had never 

 before introduced him.' 



The first comparison the stranger suggested was with Carinaria, to 

 which genus it stands closer than to any other admitted in Fischer's 

 Manuel, but from which, and from all other known Heteropods, the 

 broad wing-like expansion of the body distingidshes it. This feature 

 is well expressed in the drawings 3, 3 his, Plate Mollusques No. 3, 

 of the Atlas Histoire Naturelle of the Voyage of the " Coquille," 

 representing Pterosoma plana, Lesson. Seventy years ago the French 

 scientific expedition fished up this species between the Moluccas and 

 New Guinea, but never again, till now, had it been encountered by 

 a naturalist. 



Fischer (Man. Conch., p. 537) rejects the genus from the Mollusca 

 on the ground that it may be a pelagic Nemertine. His opinion seems 

 to be mere conjecture, and no Nemertine, so far as I can leam, 

 assumes this shape. 



I would now advance another hypothesis, — that Lesson's drawing 

 represents the animal I am about to describe, from which the shell, 

 with its contained viscera, the fin, and the proboscis, had been all torn 

 away. That this is a possible accident is shown by specimens before 

 me, from one of which the shell and its contents have been twisted 

 off, another is without a .head, and yet another has the head torn 

 half through between the eye and the tentacle, just where Lesson's 

 specimen is supposed to have been decapitated. 



One alone among half-a-dozen specimens before me has quite escaped 

 injury. All appear to be females, except one, which is certainly a 

 male. None are so large as the drawings quoted, in which G. N. 

 indicates "grandeur naturelle." Instead of 80mm., my specimens 

 measure from head to tail 30 mm., the body being 18 mm. long by 

 13 broad. The preserved specimens have now lost all their colour, 

 but Mr. Whitelegge tells me that in life a delicate rose, much as in 



' The following week the same indefatigable collector added to tlie Australian 

 molluscan roll the the pelagic Fiona marina, Forskal. 



