44 



the structure of the caudal rami, and the rather different armature of the nata- 

 tory legs. 



Occurrence. I have found this form only quite occasionally in 3 different 

 localities, viz., in the Maridal Lake near Christiania, in Mj0sen and in Tyrifjord. 

 In all 3 localities it occurred at a depth of from 2 to 6 fathoms on a muddy 

 bottom. 



Distribution. Sweden (Lilljeborg). 



23. Cyclops lueidulus, Koch. 



(PL XXV). 



Cyclops Iwidulus, Koch, 1. c. Heft 21, 10. 



Syn. : Cyclops vernalis, Fischer. 



elongatus, Claus. 



parcus, Herrick. 



Specific Characters. Female. Body comparatively slender and attenuated, 

 with the anterior division oblong oval in form, greatest width about half the 

 length and occurring somewhat in front of the middle. Lateral parts of the 

 pedigerous segments rather prominent, those of penultimate segment terminating 

 in a tooth-like projection curved outwards. Last trunk-segment rather broad, and 

 acutely produced on each side. Genital segment conspicuously dilated in front 

 and gradually tapered behind. Caudal rami rather long and slender, equalling 

 in length the last 3 segments combined, and scarcely at all divergent; seta of 

 outer edge attached not far from the end, middle apical setse long and slender, 

 the inner one exceeding the length of the tail; seta of inner corner very thin 

 and somewhat longer than that of the outer, which is rather thick, spiniform. 

 Anterior antennae scarcely longer than the cephalic segment, and generally com- 

 posed of the normal number of joints (17), though in some cases 18 joints may 

 be counted, on account of a subdivision of the 7th joint. Posterior antennae with 

 the terminal joint about the length of the penultimate one. Natatory legs com- 

 paratively strongly built, with the spines rather coarse and varying somewhat in 

 number, the terminal joint of the outer ramus having in some cases 3 spines 

 outside in one or other of the pairs instead of the usual number (2); setae of 

 inner edge of this joint in 1st pair 2, in the other pairs 3; apical spines of 

 inner ramus in 4th pair subequal in size. Last pair of legs very small, proximal 

 joint not much dilated, distal joint narrow, with the lateral spine of moderate 

 size and attached near the end. Ovisacs comparatively large, oval in form, and 

 only slightly diverging. Seminal receptacle transversely elliptical in form, and 



