_ 72 



Colour more or less dark olivaceous, with a greenish tinge ; genital 

 segment and bases of the caudal rami generally ochraceous. 



Length !of adult female scarcely exceeding I mm. 



Remarks. This appears to be the species that has been observed by 

 most authors, and to which the name Cyclops serrulatus Fischer has generally 

 been applied. It seems evident to me, indeed, that the figures given by 

 Fischer are referable to the present species; but, as the name agUix proposed 

 by Koch is of much earlier date, it must be retained for the species. Lilljeborg 

 has applied the name semdattt* to a different species, which will he described 

 below as L. Lilljeborgi, whereas he has given to the present species a new name, 

 viz., Cyclojt* rai'iu*. The latter species he again divides into 3 varieties, viz., 

 C. speratus, C. proct-imitx and C. Iraclii/nrus. The first of these supposed varieties 

 I regard as a distinct species, whereas the other 2 must be combined within the 

 species here under consideration. The C. pi'o.nmus does not differ from the 

 typical form (C. brachyurus) except in the somewhat longer caudal rami. 



Occurrence. This is a very common Cyclopid, being found everywhere 

 in small ponds and ditches, as also at the margin of large lakes. It is a very 

 active little creature, moving about with considerable speed, and thus fully 

 deserving the specific name given to it by Koch. Like the other species of the 

 present genus, it is however a true bottom-form, keeping constantly near the 

 ground, and scarcely ever being met with in company with the true lim- 

 netic species. 



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

 Algeria, Azores, Polar island north of Grinnell Land (2nd Fram Exped.), North 

 America, Australia. 



42. Leptocyelops speratus, (Lilljeborg). 



(PI. XLIV). 



Ct/rlojix rftriitH, var. speratn, Liljeborg, Synopsis speciernm generis Cyclops, p. 88, 



PI. V, figs. 1215. 



Specific Characters. Female. Rather like the preceding species, but of 

 much larger size and somewhat more slender form of body. Caudal rami 

 considerably prolonged, attaining almost the length of the last 3 segments com- 

 bined, and closely approximate throughout, not being at all divergent, outer edge 

 nearly smooth, or with only very slight traces of denticles in its posterior part; 

 middle apical setse of the usual structure, seta of inner corner considerably 

 longer than the spine of the outer. Anterior antennae very slender, reaching, 

 when reflexed, even beyond the 2nd segment, outer joints with a distinct 



