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THE GENUS PARAPLYSIA WITH DESCRIPTION OF A 
NEW SPECIES. 
By J. D. F. Gincurist, M.A., B.Sc., Pa.D. 
(Read November 29, 1899.) | 
(Plate XVI) 
The classification of the Tectibranchiata is at present in a very 
unsatisfactory state as compared with many other groups of the 
Mollusca. This is the more to be regretted as this group of animals 
is one that shows an altogether peculiar aspect of the question of 
adaption, not only to external environment but particularly to 
changes of organisation brought about by new factors arising within 
the animal itself. I have elsewhere described some of these changes 
and attempted to assign them to their causes, but much yet remains 
to be done in the mere collection of facts before any final generalisa- 
tion can be made. The mollusc now under our notice contributes 
something towards this end, and is therefore valuable not only as 
one more new species, but as a new factor to be considered in view 
of a much wider question. 
Genus Paraplysia. 
Mr. Smith has described a mollusc, from Thursday Island, Torres 
Straits, which he regards as belonging to the genus Aplysia, 
giving it the specific name piperata (Zool. Coll. Alert, p. 89). 
Subsequently another somewhat similar form from Siam was 
found in the collection of the British Museum (Natural History), 
which I described as Aplysia Mouhott (Ann. and Mag. Nat. 
Hist. (6), xv., May, 1895, p. 404). While assigning the animal 
to this genus I pointed out that these two species had several 
characters which marked them off from the other Aplysida@, and 
might entitle them to be placed in a new group. Mr. Pilsbry 
(Man. Conch. xv., p. 64) adopted this suggestion, and gave 
the generic name Paraplysia to this group. While this may be 
accepted provisionally, it will be seen, after examination of the 
specimens to be described, that some of the characters assigned to 
the group must be reconsidered. The features common to the two 
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