49 



Gen. 13. HarpaCtlCUS, M.-Edwards, 1838. 



Syn: Arpacticus, Baird. 



Generic Characters. Body slender, compressed, or slightly depressed, 

 tapering behind. Urosome normal, with none of the segments expanded laterally, 

 and considerably narrower in male than in female. Caudal rami short, more or 

 less divergent, one of the apical setoe considerably elongated. Rostrum conically 

 produced, and more or less curved downwards. Anterior antennae in female 8- or 

 9-articulate; those in male very strong, with the 1st joint divided into 2 articu- 

 lations, last joint of the proximal part globularly expanded, terminal part very 

 movable, claw-shaped. Posterior antennae with the apical spines simple, outer 

 ramus composed of only 2 joints. Posterior maxillipeds generally very powerful, 

 with the hand considerably expanded. First pair of legs with the outer ramus 

 biarticulate, and nearly twice as long as the inner, apical claws but slightly 

 curved. Inner ramus of 2nd pair of legs in male with the middle joint produced 

 at the end outside to a long deflexed mucroniform projection; 3rd pair of same 

 with the outer ramus exceedingly strong, curving more or less inwards, and having 

 the spines very coarse, whereas the natatory seta? are rudimentary. Last pair of 

 legs of moderate size, with the marginal spines, as a rule, not much prolonged, 

 distal joint oval, inner expansion of proximal joint in female comparatively broad, 

 in male rudimentary. 



Remarks. This genus was established as early as the year 1838 by 

 M.-Edwards, to include the Cyclops chelifer of 0. Fr. Miiller. Several additional 

 species have subsequently been described by different authors ; but some of these 

 species are now generally referred to other genera, or even to quite different 

 families. One of the most characteristic features by which the present genus 

 is distinguished from the 2 other genera of this family, is the peculiar trans- 

 formation in the male of the outer ramus of the 3rd pair of legs, which constitutes 

 a most powerful prehensile organ, by the aid of which, apparently, the female is 

 grasped during copulation. To the fauna of Norway belong 4 distinct species, to 

 be described below. 



32. Harpaeticus chelifer (Muller). 



(PI. XXVII & XXVIII). 

 Cyclops chelifer, 0. Fr. Miiller, Entomostraca, p. 114, PL XIX, figs. 1 3. 



Specific Characters. Female. Body pronouncedly compressed, especially 

 in its anterior part, seen dorsally, very narrow, with the greatest width quite in 



7 Crustacea. 



