S3 



outside; terminal joint of outer ramus well defined, with the apical spines of 

 moderate length. Ovisac rounded. 



Male considerably smaller and more slender than female, with the lateral 

 parts of last pecligerous segment only very slightly expanded, though on right side 

 distinctly biangular. Right anterior antenna in male with the middle section 

 moderately tumefied, antepenultimate joint of terminal section produced at the 

 end anteriorly to a straight rod-like process obtuse at the tip and extending 

 somewhat beyond the penultimate joint. Last pair of legs with the inner rami 

 well developed, though uniarticulate and acute at the tip, that of right leg 

 extending nearly to the middle of the distal joint of the outer ramus, 2nd basal 

 joint of this leg with a small hyaline lamella in the middle of the inner edge, 

 proximal joint of outer ramus produced at the end outside to a triangular pro- 

 jection, distal joint with the spine of the outer edge situated about in the middle, 

 apical claw considerably curved. Left leg extending beyond the middle of the 

 terminal joint of the right, 2nd basal joint with an appressed spiniform projection 

 inside, terminal joint produced at the end to a rather long and narrow digitiform 

 process, inside which stands a slender denticulated spine. 



Colour of female yellowish orange, that of male dark red. 



Length of adult female 1.80 mm., of male 1.40 mm. 



Remarks. In its external appearance, this form somewhat resembles D. 

 denticornis. On a closer examination, however, it may be easily distinguished by 

 the more robust form of the body, and the comparatively shorter anterior antennae, 

 but especially by the peculiar rod-like projection of the antepenultimate joint of 

 the right anterior antenna in the male. Moreover, the last pair of legs in both 

 sexes exhibit several well-marked differences. 



Occurrence. The only place where I have met with this form is in 

 the farthest north of Norway, at Vardo, Finmark. It occurred here rather 

 abundantly in a shallow tarn situated close to the town. In the same tarn the 

 arctic Phyllopod, Branchinccta paludosa, was very common, and the water was 

 moreover peopled with large shoals of Daphina magna. 



Distribution. Mountain lakes of Central Europe (Koelbel, Wierzejski), 

 British Isles (Brady), Siberia (Lilljeborg) as far north as the New Siberian Islands 

 (the present author), territory of Akrnolinsk (Lepeschkin). 



13 Crustacea. 



