52 



the right, now the left side upwards. This peculiar mode of movement has indeed 

 given rise to the specific name proposed. 



Dixt>'ibi<tio)i. Sweden (Lilljeborg), Germany (Schmeil), France (Richard). 



29. Cyclops diaphanus, Fischer. 



(PI. XXXI). 



Cyclops diaphanus, Fischer, Beitrage zur Kenntniss der in der Umgegend von St. Petersburg sich 

 findenden Cyclopiden (Fortsetzung). Bulletin Soe. Imp. Moscow : Vol. XXVI, p. 93, PI. Ill, 



figs. 6 12. 



Syn. : Cyclops nanus, G. O. Sars. 

 minutus, Glaus. 



Specific CJinrt'tctfrs. Female. Body somewhat more slender than in the 

 preceding species, with the anterior division less dilated, the greatest width 

 scarcely exceeding half the length. Lateral parts of penultimate trunk-segment 

 resembling in shape those of the 2 preceding segments. Last trunk-segment very 

 slightly produced laterally. Genital segment comparatively large and protuberant 

 below, being longer than it is broad at the base, and gradually contracted behind. 

 Caudal rarni scarcely attaining the length of the last 3 segments combined and 

 not at all divergent; seta of outer edge at a considerable distance from the apex, 

 being attached almost in the middle; inner medial seta much longer than the 

 outer, and attaining almost half the length of the body ; seta of inner corner, 

 as in C. langfidiis, very small and rudimentary. Anterior antennae scarcely as 

 long as the cephalic segment, and composed of only 11 joints. Posterior antennae 

 and maxillipeds about as in the preceding species. Natatory legs, as in that 

 species, imperfectly developed, both rami of the 1st pair and the inner one of 

 the 2nd pair being only biarticulate; rami of the 2 succeeding pairs of normal 

 structure and comparatively more slender than in C. langvidus; apical spines of 

 inner ramus in 4th pair rather elongated, the inner one attaining fully the length 

 of the terminal joint. Last pair of legs extremely small, with the proximal joint 

 imperfectly defined from the segment, distal joint narrow linear in form, with a 

 very small lateral spine near the apex. Ovisacs of moderate size and only very 

 slightly divergent. Seminal receptacle resembling in shape that in C. langridus. 



Body rather pellucid, with a faint yellow or reddish tinge. 



Length of adult female 0.70 0.90 mm. 



Remarks. Lilljeborg has pointed out that the species originally described 

 by the present author as C. nanus, is in reality identical with that recorded by 

 Fischer at a somewhat earlier date under the name C. diaphanus, and that the 

 C. minutus of Glaus is referable to the same species. Dr. Schmeil, who, how- 



