1897 - 98 .] Prof. D’Arcy W. Thompson on Marine Faunas. 331 
2050 fathoms, lat. 36° 10' N., long. 178° 0' E., in the middle of 
the North Pacific, and again in 2160 fathoms a little west of Val- 
paraiso; recorded also by Dali from 1568 fathoms in the Gulf of 
Mexico. On the grounds for accepting the West Indian specimen 
as identical with those from the Pacific, see Dali, quoted by 
Watson, Chall. Rep., Scaphopoda, p. 4. 
Jantliina rotundata , Leach. — This well-known pelagic shell of 
the North Atlantic was also taken by the “Challenger” in the 
middle of the South Atlantic, lat. 35° 41' S., long. 20° 55' W. 
Natica groenlandica , Beck. — One specimen from 75 fathoms off 
Heard Island. Watson {Rep., p. 448-) says: — “On comparing 
this Natica with G. O. Sars’ specimens from Norway, I am not 
quite satisfied, and yet I cannot part them.” He recites several 
differences between the forms, but states that “ N. groenlandica 
varies in all these respects, and the study of that species leaves the 
impression that the differences I have mentioned above might be 
found filled up.” It is notorious that the identification of the 
smaller Naticce is a matter of no little difficulty. At least three 
other closely allied species, N. xantha, N. prasina, and N. fartilis, 
Watson, all come from the same region, and the shell of the 
last named is noted by the describer as “so closely resembling 
N. affinis , G. (N. clausa , Brod. and Sow.), that I have hesitated very 
much to separate them, and have been glad to be strengthened in 
so doing by the opinion of Professor von Martens and of Mr E. A. 
Smith.” There are many other allied species of this cosmopolitan 
genus in southern waters. 
Homalogyra atomus, (Philippi). — A single, slightly weathered 
specimen dredged by the “Challenger” in 140 fathoms off Marion 
Island. This tiny shell, whose length is only *0125 of an inch, is 
widely distributed from Norway to the Mediterranean and Madeira. 
Dr Watson remarks (ifej?., “Gasteropoda,” p. 121) that it “is 
extremely abundant in Madeira, and careful search will probably 
supply many additional localities for its dwelling.” 
Odostomia rissoides, Hanley. — A common northern form re- 
corded from the neighbourhood of Marion Island. Dr Watson 
remarks {Rep., “Gasteropoda,” p. 481): — “I give this species on 
the authority of Dr Gwyn Jeffreys. I had remarked the shell’s 
great resemblance in form to O. rissoides , but the distinct and 
