33 



Colour generally light yellow or orange. 

 Length of adult female 1.50 1.70 mm. 



Remarks. The present species is in all probability identical with the 

 )rm named by Jurine Monoculus quadricornis rubens, and also Cyclops pictus 

 )f Koch may be the same species. As, however, some doubt might arise about 

 le identity, this species has generally been recorded under the name proposed 

 Fischer, who indeed was the first to give a recognisable description of it. 

 Joth C. brevicaudatus, Glaus and C. Clausi, Lubbock are undoubtedly referable 

 the present species, which may be regarded as the type of the genus Cyclops 

 defined here. 



Occurrence. This is one of our commonest Cyclopses, being very abundant 

 small ponds and tarns, especially early in the spring. It is not, like most 

 )ther species of the present genus, a strict bottom-form, but is generally found 

 lose to the surface of the water, swimming about rather quickly in the usual 

 imping manner. Male specimens are at first rather scarce, but become more 

 mmerous later in the season. Two varieties occur, the one of rather smaller 

 size than the other and of lighter colour, and found in somewhat larger tarns, 

 have, however, failed to detect any other difference between the 2 forms. 



Distribution. Throughout Europe, central and northern parts of Asia, 

 Island, Spitsbergen, Algeria. 



15. Cyclops abyssorum, G. 0. Bars. 



(PI. XVII). 

 /clops abyssorum, G. O. Sars, Oversigt af de indenlandske Ferskvandscopepoder. Chr. Vid. 



Selsk. Forhandl. 1862, p. 29. 

 Syn. : C. stremms, var. tenuipes, G. 0. Sars. 



Specific Characters. Female. Body comparatively more robust than in 

 7. strenuus, with the anterior division more tumefied in its anterior part. Cephalic 

 }gment obtusely rounded in front. Lateral parts of penultimate trunk- segment 

 jrminating in a well-marked dentiform point curving outwards. Last trunk- 

 jgment acutely produced laterally. Genital segment considerably dilated in front, 

 its greatest width exceeding the length. Caudal rami very slender and narrow, 

 exceeding somewhat in length the last 3 caudal segments combined, and rather 

 livergent, each having dorsally a very distinct longitudinal keel, inner edge coarsely 

 ciliated, seta of outer edge small and attached near the end, apical setae com- 

 )aratively longer and thinner than in C. strenuus, the inner medial one almost 

 attaining the length of the tail, seta of inner corner twice as long as that of the 

 mter. Anterior antennae much more slender and elongated than in C. strenuus, 



Crustacea. 



