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part of the tail, linear in shape and scarcely at all divergent; outer edge for the 

 greater part of its extent quite smooth, with only a short, somewhat oblique row 

 of 4 or 5 small denticles just in front of the seta of this edge; the latter rather 

 remote from the end, and attached somewhat dorsally; middle apical setae of the 

 usual structure ; seta of inner corner fully twice as long as the spine of the outer. 

 Anterior antennae much shorter than in any of the preceding species, scarcely 

 reaching, when reflexed, to the end of the cephalic segment, outer joints less 

 narrow and without any distinct lateral rib. Posterior antennae and oral parts 

 of the usual structure. Natatory legs likewise built in the usual manner; apical 

 spines of inner ramus in 4th pair rather strong and coarsely denticulate, the 

 inner one only slightly longer than the outer. Last pair of legs with the spine 

 of the inner edge very small. Ovisacs of smaller size than in the other species 

 and closely appressed to the tail. Seminal receptacle with the anterior part 

 narrowly exserted on each side. 



Colour light yellowish grey, with a faint olivaceous tinge. 



Length of adult female amounting to 1.10 mm. 



Remarks. This species was established by the present author as early 

 as the year 1863, and has been admitted by all subsequent authors. It is indeed 

 easily distinguishable by its extremely long and narrow caudal rami, which give to 

 the tail a more slender appearance than in most other Cyclopidae, a character which 

 has given rise to the specific name proposed. According to Dr. Schmeil, the 

 Cyclops maarensis of Vosseler is identical with the present species. 



Occurrence. Like the last described species, this form chiefly belongs to 

 the fauna of large lakes, occurring there in shallow water among aquatic plants. 

 It is also occasionally found in small lagunes and ponds formed by the reflux 

 of the water in these lakes. 



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

 Poland (Lande), France (Richard). 



Gen. 16. PlatyeyClOpS, G. 0. Sars, n. 



Generic Characters. Body comparatively robust, with the anterior part 

 conspicuously applanated and the epimeral parts expanded laterally. Last trunk- 

 segment short and broad, with the lateral parts more or less densely hairy. 

 Tail robust, sub-cylindric in shape, and having the genital segment comparatively 

 short and stout. Caudal rami of different shape in the different species, and 



