1898.] PLANKTON OF THE FAEEOE CHANNEL. 583 



On the Occubrence of Doliolum nationalis (Borgert) IN 

 British Waters. 



By the coartesv of Mr. E. T. Browne and of Mr. E. J. Allen, 

 the Director of the Plymouth Laboratory, I have been able to 

 examine specimens of the alleged Doliohun tritonis from Valentia 

 and Plymouth. These southern specimens prove to be D. nationalis 

 Borgert'; they differ from D. tritonis not only in their much 

 smaller size, but in the point of origin and attachment of the 

 branchial lamella. A further difference between the species, not 

 discussed by Borgert, is shown by the relations of the intestine : 

 in D. tritonis (correctly figured by Herdman -) this is short, thick, 

 and sharply curved on itself ; in D. nationalis (correctly figured 

 by Borgert, pi. v. fig. 4) it is long aud slender, and, after a nearly 

 straight course posteriorly, it is only slightly curved forwards, 

 often not so much so as he has figured. 



D. nationalis appears to be a southern and warm-water form-. 

 It has only been described hitherto from the collections of the 

 ' jS'atioual' (German Plankton Expedition) in 1889 : it was absent 

 until the ' IS'ational ' struck the true Gulf Stream (37° JN'. 59° W., 

 surface temperature 79° Eahr.) ; from there it occurred with 

 greater or less regularity t>. i-ough the Sargasso Sea, Xorth 

 Equatorial, Counter Equatorial (" Guinea Current "), and South 

 Equatorial Drifts, right up to the mouth of the English Channel 

 (49-" 7' N., 5° 8' W., surface temperature 52° Pahr.), where one 

 specimen only was captured. It appears to be only an occasional 

 visitor to our shores, probably under the influence of prevalent 

 south-westerly winds and warm weather ; it occurred at Plymouth 

 aud Valentia in 1893 ' and 1895 '. 



Parathemisto AETSSORUii (Boeck). 



This species according to Hansen ' and Sars ^ is probably identical 

 with ffyperia oblivia Krbyer ; a view now accepted by Bovallius '. 

 H. ohlivia Spence Bate, appears to be not identical with either of 

 the above. 



Its distribution vertically and horizontally is a Uttle perplexing, 

 so far as our information goes at present. 



i. It lives in cold water, apparently at the surface, in Greenland 

 seas (Kroyer ' and Hansen °), and in the Murmanske Hav, North 

 of Russian Lapland (Hansen '). 



ii. It lives in cold water at great depths— from 1710 to 160 



^ Op. cit. p. 581 supra. 



^ Op. cit. p. 581 supra, pi. xx. fig. 1. 



^ W. Grarstang : Journ. Mar. Biol. Assoc, iii. p. 222. See also p. 210 for an 

 account of the weather that j'sar. 



* E. T. Browne : Journ. Mar. Biol. Assoc, iv. p. 171. 



* Hansen : Malacostraca marina GroBnlandise occidentalis. 

 ' G. O. Sars: Crustacea of Norway, vol. i. p. 11. 



'' BoTallius : Xoiigl. Svenska Vetenskaps-Akad. Hdig. xxi. p. 251. 



* Kroyer : " Gronlands Amfipoder," Vidensk. Selsk., nat.-math. Afh.vii. p. 229. 

 ^ Hansen : Dijmphna Togtets 2ool.-bot. Udbytte, 1886, Krebsdyr, p. 28. 



