646 PROF. F. J, BELL ON THE GENUS PsoLUs.  [Nov. 14, 
not been able to detect, in what is called P. sqguamatus, those cup- 
shaped spicules which are so well-known in P. fabricii; nor would 
they seem to have been seen by Diiben and Koren, who, at any rate, 
do not figure them. This, of course, is only negative evidence ; and, 
indeed, the whole discussion is a somewhat barren one until a large 
series of forms of all sizes can be brought together. 
PsoLus ANTARCTICUS. 
In connexion with the discussion which is raised under the head 
of P. fabricii as to the extent of the area of distribution of that 
northern form, and the words of Philippi when describing the south- 
ern form, “ diese Art ist der Holothuria squamata, O. Fr. Mill., so 
ahnlich, dass ich lange gezweifelt habe, ob ich sie nicht ohne weite- 
res dafiir ansprechen sollte,’ it may be well to state explicitly what 
the differential characters appear to be. 
(1) The body is much more flattened, or compressed from above 
downwards, instead of from side to side; very small examples are 
quite flat. 
(2) The oral and anal valves are very much larger; and there is, 
as Philippi has already remarked, very much greater regularity in 
their arrangement. 
(3) The bare integument on the trivial surface is very much 
thinner, and is in young specimens quite transparent. 
(4) The scales are larger, and therefore less numerous: they are 
also much less granulated ; but this is a character which varies so 
much within the range of a species that too much value must not 
be set on it. 
On the whole, perhaps, P. antarcticus is as distinctly marked a 
species as any in the genus. 
Psouus REGALIS. 
The description given by Ayres of the internal characters of this 
species is so exact, that one regrets that he was not acquainted with 
the work of Grube, in which the name Psolus granulatus had been 
given to a totally different animal. 
So far as the specimens now before me allow of an opinion, it 
would seem that even the external form is sufficient to distinguish 
the species from P. phantapus. PP. regalis is longer and narrower, 
and the elongate-conical “tail” is much more nearly the result of a 
gradual tapering of the body ; the granulation is much more evenly 
diffused, and there are no signs at all of any large plates. 
The specimens in the national collection were presented by the 
Nova-Scotia Commissioners, and are all of large size. 
PsoLus PHANTAPUS. 
Prof. Duncan and Mr. Sladen (op. cit.) direct attention to the re- 
semblance between the young of P. fabricii and of this species, basing 
their remarks, as I understand, on specimens, a few millimetres long, 
which were determined by the Rev. A. M. Norman as the young of 
P. phantapus. Such of these examples as are in the British Museum 
