siderably divergent. Seminal receptacle with the anterior part transversely ellip- 

 tical in form and sharply defined from the posterior part, which is exserted on 

 jach side to a band-like stripe. 



Colour rather variable, in some cases bluish green, in other cases with 

 a distinct olivaceous tinge, and not uncommonly light whitish grey, with dark 

 mtches at the end of the segments. 



Length of adult female amounting to 1.90 mm. 



Remarks. This form has generally been recorded under the name 

 C. viridis Jurine. I consider it, however, to be scarcely admissible to appropriate 

 as specific designations the several varietal names appended by Jurine to his species 

 Monoculus qvadricornis and merely indicating the diversity in colour found by 

 him in different specimens. As moreover the colour both in the present species 

 ind in several other Cyclopses is rather variable, the Jurinian names would in 

 ict be of very little significance to the species. The form recorded by Koch as 

 C. rulgaris is unquestionably this species, and as the name viridis applied to the 

 species by Fischer is of much later date, it must cede to that proposed by Koch. 

 C. brevicornis of Glaus is likewise identical with the present species. On the 

 other hand, the North American form named by Herrick C. viridis var. ameri- 

 ma, is scarcely the same species, as the armature of the natatory legs is 

 essentially different. 



The present species, which belongs to the group of Cyclopses distinguished 

 by Dr. Schmeil as the bicuspidatus group, may be easily recognised by its 

 )mparatively robust body, the large divergent ovisacs, and the peculiar structure 

 )f the last pair of legs. 



Occurrence. It is one of our commonest Cyclopses, and thus fully deserves 

 le specific name proposed for it by Koch. I have met with it at all seasons 

 )f the year, both in. small ponds and ditches and in larger lakes, where it descends 

 rather considerable depths. 



Distribution. Sweden (Lilljeborg), British Isles (Brady), Germany (Schmeil), 

 ''ranee (Richard), Russia (Fischer), Central Asia and Siberia (the present author). 



21. Cyclops gigas, Glaus. 



(PI. XXIII). 



Cyclops gigas, Glaus, Weitere Mittheilungen iiber Cyclopiden ; Arch. Nat. Hist 23 Jahrg, B. 1 



p. 201, PI. XI, figs. 15. 

 Syn. : Cyclops ingens, Herrick. 



Specific Characters. Female. Body much larger than in C. vulgaris and 

 of a somewhat more slender form, though otherwise exhibiting a very similar 



Crustacea. 



