209 



The species in question differs in so many important 

 cliaracteristics, especially in the 5th pairs of legs and the 

 masticatory apparatus, from the type-species that I am 

 inclined to form for it a new genus, for which I should like to 

 propose the name Psc'iuloH'olfciflirix. 



Xanthocalanus fragilis, Aurivilhus. 



Gicsbicclif has described from the Mediterranean two species 

 of this genus, viz., A', (igilis and A', minor, which, according to 

 G. 0. Sars, however do not represent more than one species, 

 A', minor being founded on young specimens. Aurivilliiis 

 added in 1898 two other species, X. fi{ii>ilis and X. simpUw. In 

 1900 G. 0. Sars described from the Polar Basin a form found 

 by Xanscn and named A', boicalis. .So far I can see there is no 

 essential difference between X. fiagilis and A', boreal is. The same 

 form was found by T. Scoff at Shetland, and the specimens I 

 found in the South African Seas are evidently of the same kind, 

 their fifth pair of legs being 2-jointed. Later Professor G. 0. 

 Sc//'5 describes more fully in the Crustacea of Norway Calanoida, 

 A', borealis, which, in full-grown specimens, has 3-jointed 5th 

 pair of legs with 4, not 3 terminal spines. Besides, the right leg 

 of the 5th pairs of the male is rudimentary or wanting. In the 

 species of Aurivilhus the right leg is nearly as long as the left 

 one. It seems to me possible that two nearly allied species have 

 been confounded. In all cases the specimens from South 

 Africa did not differ essentially from the description of 

 Aurivilhus. All my specimens were females, in length 2,9 

 millim. (Norwegian specimens 3,50 millim, from the Polar 

 Basin 4 millim, according to G. O. Sars ; Aurivilhus gives no 

 measures for the female, but for the male 2,5 millim). 



I. C.Thompson has described under the name of A', gies- 

 brechfi (Ann. Mag. Nat. Hist. [7] XII. p. 22, P. IV., f. 1-9, 

 1903) another apparently very nearly allied form, found 

 west of Ireland in a haul from 2580 m. In case the illustration 

 be correct one cannot identify it with X. fragilis as the anterior 

 antenna reach beyond the furca, but in X. fragilis scarcely 

 beyond the genital segment. 



There were in the collections I have received still some few 

 new species, in parts belonging to new genera, but the rare 

 specimens I have hitherto found were too incomplete for a 

 full description. 



