ructure those in C. lacustris. Natatory legs armed as in the 3 preceding species, 

 ii moderately slender, the inner one in 4th pair with the outer apical spine 

 jry small; spines of outer ramus in all pairs rather thin; seta attached inside 

 1st basal joint in 4th pair much coarser than in the other pairs. Last pair 

 of legs with the proximal joint comparatively small, distal joint more than twice 

 as long, with the lateral spine of moderate size and attached somewhat beyond 

 the middle. Ovisacs generally very small, rounded, each containing a very limited 

 number of ova. Seminal receptacle of moderate size and evenly rounded both 

 in front and behind. Spermatophores attached to the genital opening unusually 

 large, projecting beyond the side of the genital segment. 



Body highly pellucid and generally almost colourless, in some cases, 

 however, exhibiting a beautiful emerald green hue. 



Length of adult female 1.20 1.40 mm, of male 1.10 mm. 



Remarks. This form was considered by Dr. Schmeil as only a variety of 

 C. strenuus; but Lilljeborg has subsequently, in his account of the Swedish Cy- 

 clopses, vindicated its specific distinctness. It is especially recognisable by the 

 extraordinary development in the female of the epimeral plates on the last 2 

 trunk-segments, which gives the body a rather characteristic appearance and 

 has indeed given rise to the specific name scutifer. 



Occurrence. I have met with this form rather abundantly in several of 

 our larger lakes, for instance in the Maridal and Lut Lakes near Christiania, where 

 it lives as a true limnetic form. It also occurs in mountain lakes at the limit 

 of perpetual snow, and is indeed the only Crustacean to be found there. 



Distribution. Sweden (Lilljeborg), Northern part of Siberia (the present 

 author). 



18 Cyclops vicinUS, Uljanin. 



(PI. XX). 

 Cyclops vicinus, Uljanin, Crustacea of the Expedition of A. Fedtschenko in Turkestan (in Russian). 



p. 30, PI. X, figs. 17. 



Syn.: Cyclops strenuus, Schmeil (not Fischer). 

 pulchellus, Brady (not Koch). 



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

 division oblong oval in form and somewhat tumefied in front. Lateral parts of 

 penultimate trunk-segment produced in the form of acutely triangular extant 

 lappets; those of last segment likewise produced, though less so than in C. scutifer. 

 Genital segment about as long as it is broad at the base, and gradually narrowed 

 behind. Caudal rami long and slender, equalling in length the last 3 segments 



