49 



tumid, being scarcely longer than it is broad. Caudal rami narrow and some- 

 what tapered, being about as long as the last 3 segments combined and not at 

 all diverging; seta of outer edge not far from the apex, middle apical setse 

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

 very small, shorter than that of .the outer. Anterior antennae scarcely as long 

 as the cephalic segment, and 17-articulate. Posterior antennae with the terminal 

 joint a little longer than the penultimate one. Maxillipeds of the usual structure. 

 Natatory legs exhibiting a similar armature to that in the preceding species ; rami, 

 however, comparatively shorter; terminal joint of inner ramus in 4th pair scarcely 

 longer than the middle one, and having the outer apical spine shorter than the 

 inner. Last pair of legs somewhat resembling those in C. pulchellus, though 

 having the distal joint comparatively shorter and the lateral spine less produced. 

 Ovisacs rather large, oval in form, and only slightly divergent. Seminal receptacle 

 with the anterior part surrounded by a clear area forming on each side an 

 auricular corner, posterior part somewhat produced and evenly rounded. 



Colour whitish grey, with a more or less distinct reddish or brownish tinge. 



Length of adult female 1.00 to 1.25 mm. 



Remarks. This form was formerly erroneously identified by the present 

 author with C. Ucuspidatus Glaus, which belongs to the preceding species. It 

 has subsequently been described by Dr. Rehberg as C. bisetosus. and this name 

 is now generally adopted for the present species. In its external appearance it 

 has a general resemblance to C. pulchellus, but is of somewhat smaller size, and 

 is moreover distinguished by some differences in the structure of the caudal rami 

 and legs, as also in the manner in which the ovisacs are carried in relation to 

 .the axis of the body. 



Occurrence. This species is by no means uncommon. I have taken it 

 in many parts of the country, and always in very shallow pools and ditches, 

 which are subjected to more or less complete exsiccation during the summer. 



Distribution. Sweden (Lilljeborg), Germany ^Schmeil), Siberia (G. 0. 

 Sars), Spitsbergen (Richard). 



27. Cyclops crassicaudis, G. 0. Sars. 



(PI. XXIX). 

 Cyclops crassicaudis, G. 0. Sars, 1. c., p. 40. 



Specific Characters. Female. Body less slender than in the preceding- 

 species, 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 trunk-segments somewhat prominent. Last trunk-segment rather broad, 



7 Crustacea. 



