86 



on the tip 2 unequal spines, one of them rather slender and elongated; terminal 

 joint of outer ramus well defined though very small, inner apical spine about 3 

 times as long as the outer. Ovisac very large and oval in form. 



Male considerably smaller and more slender than female, with the lateral 

 parts of last pedigerous segment less expanded, though, as in the female, bifurcate 

 at the tip. Eight anterior antenna with the middle section considerably tumefied, 

 terminal section without any projections or denticles. Last pair of legs with the 

 inner ramus developed almost equally on both sides, that of right leg reaching 

 beyond the 1st joint of the outer ramus, 2nd basal joint of same leg with a 

 hyaline lamella inside in the middle, proximal joint of outer ramus acutely pro- 

 duced at the end outside, distal joint with the spine of the outer edge placed in 

 front of the middle ; apical claw very strong and evenly curved. Left leg scarcely 

 reaching beyond the penultimate joint of the right, terminal joint rounded, finely 

 ciliated inside and projecting at the tip in a quite short, digitiform process, inside 

 which a short blunt spine is fixed. 



Colour of female generally yellowish or orange, that of male more reddish. 

 Usual length of adult female 2.10 mm., of male 1.90 mm. 



Remarks. This form was described as early as the year 1820 by Jurine 

 as Monoculus castor. The Glaucea rubens of Koch seems to be the same species, 

 and it is very probable that the 3 forms recorded by 0. Fr. Muller as Cyclops 

 coerulcus, rubens and lacinulatus are also referable to the present species. It 

 is the largest of our Diaptomi, and is moreover easily recognized by its com- 

 paratively robust body, the form of the lateral expansions of the last pedigerous 

 segment, and that of the genital segment in the female, and finally, by the 

 unusually short anterior antennae. 



Occurrence. I have hitherto only met with this form in 4 localities, 3 of 

 which belong to the southern part of Norway, viz., Sandosund, Fredriksvscrn, 

 Mscrdo, whereas the 4th, Tjoto, is located much farther north, on the Nordland 

 coast. In all 4 places it only occurred in shallow pools of small dimensions. 



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

 Switzerland (Jurine), France (Richard), Spain (Bolivar}. 



