SMITH : ON ARCTIC AND ANTARCTIC MOLLUSCA. 165 
or fold, and they are of a different texture. It is one of those cases 
of uncertainty which arise through a very close resemblance, and 
which would probably be cleared up if we had a good series of 
specimens for comparison. 
9. Puncruretta Noacuina (Linneeus).—This well-known northern 
form was obtained by the ‘‘ Challenger ”’ expedition at four stations in 
the Kerguelen region, also in the Straits of Magellan. Conchologically 
there seems to be no reason for separating the specimens obtained at 
these localities. ‘Lhe species has, however, such a wide range in 
Northern seas, the west coast of North America, Japan, etc., that 
its occurrence anywhere would not be surprising. Moreover, there 
are several not very dissimilar forms known from the West Indian 
region, and the genus occurs in all four quarters of the globe. 
To quote another example of wide range in the genus | would refer 
to Puncturella Asturiana of Fischer, which is known from the Bay of 
Biscay, the West Indies, and off the west coast of Ceylon. 
10. Trocnus (Margarita) InrunprsuLum, Watson.— A beautiful deep- 
water species from off Bermuda, 1,075 fathoms; off Marion Island in 
the Southern Ocean in 1,375 fathoms (‘‘ Challenger”); 100 miles 
eastward of the entrance to Chesapeake Bay, 1,685 fathoms (Dall) ; 
Gulf of Manaar, Ceylon, 738 fathoms (‘‘ Investigator’). 
Slight differences, as might be expected, are observable in the 
specimens from these localities, still not sufticient to give them distinct 
specific rank. It will be noticed that all are from great depths, 
where cases of very remarkable distribution have been shown to occur. 
11. ? Doris tTuBERcULATA, Cuvier. — This well-known northern 
Nudibranch was quoted by myself from Kerguelen Island in the 
Report upon the Mollusca obtained by the ‘Transit of Venus Expe- 
dition’’ to that island, the identification resting upon the authority of 
Mr. P. 8. Abraham, who at the time had been naming the species 
in the Museum collection. But a greater master in the study of 
the Nudibranchiata, Dr. Rudolf Bergh of Copenhagen, has since 
declared this form to be both generically and specifically distinct, 
and designated it with the name ef Archidoris Kerguelenensis. This 
species was also found by the ‘‘ Southern Cross”’ naturalists at Cape 
Adare, Victoria Land. 
This concludes the discussion of the individual species under con- 
sideration, and | will now try to summarize the result. 
In the first place six out of the eleven species are probably wrongly 
identified, namely, the Glomus, Kellia, Homalogyra, Natica, Odostomia, 
and Doris. Excepting in the case of the Loris the identifications 
were based upon either one or two specimens, and all, with the 
exception of the Watica, are very small and insignificant, without any 
striking features, so that it becomes quite impossible to decide their 
identification with any approach to certainty. 
Of the remaining five species, whose determination appears to be 
admissible, the /anthina, being pelagic, scarcely comes within the 
scope of the discussion, the Myfi/us is almost cosmopolitan, the 
