91 



Occurrence. I have met with this form in several of the Norwegian 

 mountain lakes, for instance, Aursundsjo, Afsjo, Gaavelivancl, Lesjevand, as also 

 in some lakes in the districts of Romsdal and Trondhjem; and Mr. Huitfeklt-Kaas 

 has recently found it in several lakes in the western part of the country. 



Distribution. Jemtland, Sweden (Lilljeborg). 



38. Diaptomus laeiniatus, Lilljeborg. 



(PI. LXII). 



Diaptomus ladniatm, Lilljeborg, in J. de Guerne and J. Richard, Revision des Calanides d'eau 



douce, p. 47, PL 1, figs. 22, 24, 25. 



Specific Characters. Female. Body somewhat robust of form. Anterior divi- 

 sion, seen dorsally, oblong oval in outline, greatest width considerably exceeding 

 Yn of the length and occurring somewhat in front of the middle, anterior extremity 

 rounded, posterior somewhat irregular. Last 2 segments of metasome confluent 

 dorsally, and each produced laterally to very conspicuous extant linguiform lobes, 

 the anterior pair obtuse at the tip, the posterior acuminate. Urosome compara- 

 tively short, genital segment slightly dilated in front, but without any lateral 

 denticles. Caudal rami scarcely twice as long as they are broad. Anterior 

 antennae, when reflexed, extending to about the base of the caudal rami. Last 

 pair of legs with a distinct triangular projection on the hind face of 1st basal 

 joint, inner ramus uniarticulate and extending almost to the end of the 1st joint 

 of the outer, tip acutely produced, terminal joint well denned, with the apical 

 spines comparatively short. Ovisac rounded and, as a rule, containing only a 

 limited number of ova. 



Male of the usual appearance, with the last 2 pedigerous segments well 

 denned and not expanded laterally. Terminal part of right anterior antenna 

 simple, without any projection of the antepenultimate joint. Last pair of legs 

 with the inner edge of 2nd basal joint quite smooth, without any projecting 

 lamella, inner ramus of right leg somewhat larger than that of left, and extending 

 almost to the tip of the distal joint of the outer ramus, proximal joint of the 

 latter produced at the end outside to a comparatively short triangular projection, 

 distal joint with the spine of the outer edge situated about in the middle, apical 

 claw greatly curved. Left leg extending beyond the middle of the terminal joint 

 of the outer, last joint produced at the end to a comparatively short and blunt 

 digitiform process, on the inner side of which there is a similarly short spine. 



Colour sometimes dark bluish, sometimes reddish orange. 



Length of adult female 1.60 mm., of male 1.40 mm. 



