92 



Remarks. The female of this species is at once recognized by the peculiar 

 shape of the last 2 pedigerous segments, both of which are produced laterally to 

 very conspicuous, freely-projecting expansions separated on each side by a narrow 

 incision. Otherwise it is nearly allied to D. laticeps, differing somewhat, however, 

 in the structure of the last pair of legs in both sexes, as also in the total absence 

 of any projection on the antepenultimate joint of the right anterior antenna in 

 the male. 



Occurrence. Prof. Lilljeborg first found this form in a small lake situated 

 on the summit of the Floifjeld near Bergen, and also received it from the Oster- 

 clal through Miss B. Esmark. I have myself met with it in many places in the 

 country, both in lowland and in mountain lakes, and, according to the recent 

 investigations of Mr. Huitfeldt-Kaas, it is generally distributed in the lakes of 

 western Norway. The most northern locality where I have found it is the 

 mainland opposite Vardo, Finmark. It here occurred very abundantly in shallow 

 tarns together with Hcterocope borealis and 2 Phyllopods, viz., Brancliinccta paludosa 

 and Polyartemia forcipata. All the specimens occurring here were of a dark 

 reddish orange hue, whereas those from other tracts more .generally exhibited a 

 bluish colour. 



Distribution. Scotland (Scott), Lake of Geneva (Cleve), Russian Lapland 

 and the Kola Peninsula (Lilljeborg). 



39. Diaptomus gracilis, G. 0. Surs. 



(PI. LXIII). 



Diaptomus gracilis, G. O. Sars. Oversigt. af de indenlandske Ferskvandscopepoder. 



Chr. Vid. Selsk. Forh. 1862, p. 9. 



Syn: Diaptomus Westwoodi, Lubbock. 



Specific Character Female. Body very slender in form, with the anterior 

 division, seen dorsally, narrow oblong in form, greatest width not attaining y 3 of the 

 length, and occurring about in the middle, anterior extremity considerably contracted, 

 posterior subtruncate. Lateral expansions of last pedigerous segment very distinctly 

 biangular, each corner tipped with an acute denticle, the outer one rather produced 

 and pointing straight outwards. Genital segment somewhat longer than the other 2 

 caudal segments combined, and gradually dilated in front, with a very conspicuous 

 acute denticle on each side. Caudal rami comparatively short, being scarcely 

 more than twice as long as they are broad. Anterior antennae exceedingly slender 

 and elongated, extending, when reflexed, far beyond the caudal rami, in some cases 

 by as much as the 4 or 5 outer joints, in other cases by only 3 of the joints. 



