94 



Occurrence. In the southern part of Norway this is one of the commonest 

 Diaptomi, occurring very abundantly in almost all the larger lowland lakes, and 

 constituting there the essential bulk of the zooplankton. 



Distribution. Sweden (Lilljeborg), Finland (Nordquist), British Isles (Lub- 

 bock), Germany (Schmeil), Switzerland (Imhof), Hungary (Daclay), Italy (Pavesi). 



40. Diaptomus graciloides, Lilljeborg. 



(PL LXIV). 



Diaptomus graciloides, Lilljeborg. Description de deux nouvelles especes de Diaptomus da Nonl 

 de 1'Europe. Bull. Soc. Zool. France, Vol. XIII, p. 156. 



S2)ecific Characters Female. Very like the preceding species, but some- 

 what less slender in form, and also of rather inferior size. Lateral parts of last 

 pedigerous segment but very slightly expanded and not at all extant, being 

 rounded off at the tip, though exhibiting the 2 usual denticles, which however are 

 much smaller than in D. gracilis. Genital segment rather narrow, being far less 

 dilated in its anterior part than in the above species, lateral denticles extremely 

 small. Caudal rami about as in D. gracilis Anterior antennae very slender and 

 elongated, reaching, when reflexed, considerably beyond the caudal ram^(by about 

 the 2 or 3 outer joints). Last pair of legs with a very small, somewhat linguiform 

 projection on the hind face of the 1st basal joint, inner ramus imperfectly biarti- 

 culate, and reaching somewhat beyond the 1st joint of the outer ramus, terminal 

 joint of the latter well defined, though somewhat smaller than in D. gracilis, inner 

 apical spines, as in that species, very slender, extending as far as the tip of the 

 unguiform projection of the preceding joint. Ovisac small, with a very limited 

 number of ova. 



Male resembling that of D. gracilis, though somewhat less slender. 

 Antepenultimate joint of right anterior antenna without any trace of a projection 

 at the end. Last pair of legs comparatively less powerful than in D. gracilis, 

 inner rami of about equal size and simple cylindric in form, that of right leg not 

 extending to the middle of the distal joint of the outer ramus, proximal joint 

 of the latter very slightly produced at the end outside, distal joint much smaller 

 than in D. gracilis, with the spine of the outer edge situated beyond the middle, 

 apical claw irregularly flexuous. Left leg extending far beyond the penultimate 

 joint of the right, inner edge of 2nd basal joint perfectly smooth, terminal joint 

 of a similar form to that in D. gracilis, but with the seta of the inner edge not 

 penicillate, and extended straight downwards. 



