SIR CHARLES ELIOT. 



species of each genus being much smaller than the first. The differences in the radulse 

 may be due to growth, for in both genera the teeth near the rhachis are very irregular 

 and undefined in outline. 



With the exception of Tritonia challenger iana, already recorded from the west coast 

 of Patagonia, all the forms appear to be new. Some uncertainty must exist about Doto 

 antarctica, which greatly resembles Doto frag His, but there are some points of difference 

 and it seems safer to create a new species, for it is a considerable assumption to take for 

 granted that similar forms from northern and southern seas are specifically identical. 



The Nudibrauchiata of the Arctic and Antarctic oceans with their neighbouring 

 waters show considerable general resemblances, as far as the faunas are known. There 

 is a marked scarcity of Dorids and a preponderance of Tritonids and Aeolids. It must 

 be remembered, however, that Dorids are most abundant under large stones in the littoral 

 zone, and that even if they exist in such localities on ice-bound shores, they are not 

 likely to be brought up by the dredge. But it would seem that even in accessible 

 waters they decrease in numbers towards the extreme south. A collection of Nudi- 

 branchs made in the Falkland Islands contains only five Dorids referable to two 

 species, but nearly forty Aeolids, referable to about four species, and seven Tritonids. 

 The ' Belgica ' obtained only Tergipes antarcticus. The present collection and that 

 made by the Scottish National Antarctic Expedition have together yielded eleven 

 specimens of Tritonids, eight of Notaeolidia, one of Doto, eight of various Aeolids, two 

 of Bathydoris, and no ordinary Dorids at all. Acanthodoris, however (which with 

 the allied Adalaria has been found far north in both the Pacific and Atlantic), is 

 recorded from New Zealand and Cape Horn (Rochebrune and Mabille), and probably 

 extends further south. Archidoris is recorded from Kerguelen Island, Cape Adare 

 and Wandel Island.* 



The two collections are too small to warrant any conclusions as to the absence of 

 forms which are not represented, but, as far as they go, they indicate that the Arctic 

 and Antarctic Nudibranchs are similar rather than identical. As for species, Dr. Bergh 

 regards an Acanthodoris found in New Zealand as a variety of A. pilosa, and the 

 animal here described as Doto antarctica may possibly be a variety of D. fragilis. The 

 genera Tritonia and Bathydoris are common to both seas, and are also recorded from 

 intermediate points, Bathydoris only from great depths. Tritoniella, Tritoniopsis, and 

 Notaeolidia are recorded only from the south, while Dendronotus and Campaspe, 

 though frequent in both the North Atlantic and North Pacific, and extending into the 

 Polar regions, are not recorded from further south than the Bay of Biscay and 

 California. The Antarctic Aeolids hitherto collected are allied to Cratena or Galvina, 

 no Facelinidse or Coryphellidse having been found. It is remarkable that in all of 

 them the vent is dorsal, not lateral. 



* M. Vayssiere (Bull, du Mus. d'Hist. Nat., (1906), 3. p. 147) gives preliminary diagnoses of the four Nudi- 

 branchs found by the ' Charcot ' Antarctic Expedition (64 to 65 lat. S. and 64 long. W.). They are Archidoris 

 tuberculata ; Guy-Valvoria [sic. Ed.] , a new genus of the Aeolididse ; Charcotia, which apparently unites some 

 of the characters of the Tritoniidse and Tethymelibidse ; and Notaeolidia gigas. 



