50 



being produced on each side to an acuminate projection pointing outwards. Tail 

 comparatively short and thick, exceeding only very slightly half the length of 

 the anterior division; genital segment unusually dilated throughout its whole 

 length, exhibiting a slight constriction in front of the middle. Caudal rami of 

 moderate size, about equalling in length the last 2 segments combined, and scarcely 

 at all divergent; seta of outer edge not far from the apex, middle apical setae 

 slender, the inner one exceeding the length of the tail; seta of inner corner 

 extremely small and rudimentary, scarcely more than half as long as that of the 

 outer. Anterior antennae about the length of the cephalic segment, and com- 

 posed of only 12 joints, the 8th and 9th joints, as in C. capillatus, answering to 

 the 7 short articulations succeeding the 7th joint in other species. Posterior 

 antennae and maxillipeds about as in the preceding species. Natatory legs un- 

 usually short and stout, with the joints of the rami broad and expanded, number 

 of spines and setae as in the 2 preceding species; inner ramus of 1st pair with 

 the apical spine unusually strong and somewhat curved, that of 4th pair with the 

 terminal joint scarcely longer than the middle one, and having the inner apical 

 spine longer than the outer. Last pair of legs resembling in shape those in C. bise- 

 tosus. Ovisacs rather large, oblong oval in form, and slightly divergent. Seminal 

 receptacle with the anterior part somewhat expanded laterally, posterior part only 

 slightly produced. Spermatophores attached to the genital opening of quite unusual 

 size, kidney-shaped and placed close together longitudinally to the axis of the body. 



Colour uniformly whitish grey. 



Length of adult female 0.90 1.10 mm. 



Remarks. This form ranges among the smaller species of the present 

 genus, and may readily be recognised by its comparatively short and stout tail, 

 which character indeed has given rise to the specific name proposed. In the 

 structural details also it exhibits several well-marked differences from the species 

 described in the preceding pages. 



Occurrence. I have taken this form occasionally in shallow pools and 

 ditches near Christiania. It is not very active in its motions, and in this respect 

 somewhat resembles the next species. 



Distribution. Sweden (Lilljeborg), Bohemia (Schmeil). 



' 



28. Cyclops langvidus, G. 0. Sars. 



(PI. XXX). 

 Cyclops langvidus, G-. 0. Sars, 1. c., p. 40. 



Specific Characters. Female. Body moderately slender, with the anterior 

 division oval in form, greatest width somewhat exceeding half the length and 



