41 



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

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

 each 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 

 patches 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 qvadrieornis and merely indicating the diversity in colour found by 

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

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

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

 C. vulgaris is unquestionably this species, and as the name riri<Hx applied to the 

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

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

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

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

 essentially different. 



The present species, which belongs to the group of ( 'yclopses distinguished 

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

 comparatively robust body, the large divergent ovisacs, and the peculiar structure 

 of the last pair of legs. 



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

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

 of the year, both in small ponds and ditches and in larger lakes, where it descends 

 to rather considerable depths. 



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

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



21. Cyclops gigas, Glaus. 



(PI. XXIII). 



Cyclops gigas, Claus, Weitere Mittheilungen fiber 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 



G Crustacea. 



