124 



sionally it however also occurs farther south off the west coast of Norway, 

 thus in the neighbourhood of Christiaiisund (M. Sars), and at Karmo (Boeck). 

 Distribution. -- Arctic Ocean widely distributed: Greenland, Spitsbergen, 

 the Murman coast, the White Sea, Matotschkin Schar, the Kara Sea, the 

 Siberian Polar Sea; Labrador; Kattegat, the Baltic. 



2, Pontoporeia affinis, (Lindstrom). 



(PI. 41, fig. 2). 

 Pontoporeia affinis, Lindstrom, 0fvers. af Kgl. Vet. Akad. Forhandl. 1855, p 63. 



Body somewhat more compressed than in the preceding species, but 

 otherwise rather similar in appearance. Cephalon considerably longer than 

 the 2 first segments of mesosome combined, lateral corners narrowly rounded 

 at the tip. Coxal plates without any dentiform projection at the infero-posteal 

 corner; 1st pair but slightly expanded distally, and scarcely broader than the 

 succeeding ones ; 5th pair with the anterior lobe not nearly so deep as in 

 P. femorata. Last pair of epimeral plates of metasome nearly right-angled. 

 First segment of urosome without any trace of a dorsal process. Both the 

 metasome and urosome provided dorsally with scattered hair. Eyes small, 

 oval, pigment black. Superior antennae in female with the flagellum about as 

 long as the peduncle, accessory appendage longer than the last joint of the 

 peduncle, and triarticulate. Flagella of both pairs of antennae in male consi- 

 derably more elongate than in female, and divided into a much greater num- 

 ber of articulations. Anterior gnathopoda with the outer joints far less expan- 

 ded than in P. femorata, propodos narrow oval, the inferior edge but very 

 slightly bulging out behind the middle. Posterior gnathopoda with the pro- 

 podos about as long as the carpus. Last pair of pereiopoda with the basal 

 joint somewhat less expanded than in the preceding species, and scarcely lon- 

 ger than the remaining part of the leg. Last pair of uropoda in female very 

 small, outer ramus with only 3 spines exteriorly. Telson likewise very small, 

 more broad than long, cleft extending about to the middle. Colour yellowish, 

 with a more or less distinct tinge of orange ; body-segments often bordered 

 with dark bluish green. Length of adult female scarcely exceeding 8mm. 



Remarks. - Although rather nearly allied to the preceding species, 

 this form is at once distinguished, not only by its much smaller size, but also 

 by the absolute want of any dorsal process on the urosome, and by the dark 

 ocular pigment. 



Occurrence. - In Norway this form is exclusively a fresh water species, 

 being only found in true lakes, thus in Sognsvand and Elvvaagen in the 

 neighbourhood of Christiania, as also in Orrevand on Jsederen. It here occurs, 



