505 



relict form, since it occurs abundantly in lakes lying from 3000 to 4000 

 feet above the level of the sea. I have found it in numerous places up 

 to Finmark, generally in greater lakes, but occasionally also in smaller ponds, 

 as also in tranquil dilatations of rivers, for instance in Laugen, at its junction 

 with the Otta river. In nearly all our mountain-lakes it occurs in great 

 numbers, constituting there a substantial food for the trout 



Distribution. Sweden (De Geer), British Isles (Pennant), Holland 

 (Hoek), Germany (Koch), Russia, Siberia (Brandt). 



Gen. 6. Pallasiella, G. 0. Sars. 



Syn. : Pallasia, Sp. Bate. 



Body narrow and elongated, with the segments sharply marked off 

 from each other, and more or less spiny, those of urosome smooth above, 

 without any fascicles of spinules. Cephalon without any distinct rostrum, but 

 having on each side a tuberculiform projection. Coxal plates not very large, and 

 somewhat protuberant laterally. Eyes large and prominent. Superior antennae 

 longer than the inferior, with the peduncle very much elongated, and the 

 accessory appendage poorly developed. Oral parts normal. Gnathopoda rather 

 powerful, and but little different in the 2 sexes, though being, as usual, 

 somewhat more strongly built in the male. Pereiopoda slender and elongated, 

 basal joint of the 3 posterior pairs rather large, especially that of the last pair. 

 The 2 anterior pairs of uropoda very unequal in size, the penultimate pair 

 being unusually small, both pairs having the rami subequal and mucroniform, 

 nearly destitute of spines. Last pair of uropoda somewhat projecting beyond 

 the others, rami more or less unequal, the outer one being generally much the 

 larger, and ha,ving the terminal joint extremely small. Telson not bipartite, 

 but only more or less incised at the tip. 



Remarks. - - This genus was established by Sp. Bate, to include an arctic 

 species, Gammarus canceUiis of Pallas. As, however, the generic name he pro- 

 posed was already appropriated in zoology, I have substituted the diminutive 

 form. It is nearly allied to the gen. Gammarus, differing however by the narrow 

 and more or less spinous body, by the absence of any fascicles of spinules 

 on the dorsal face of the urosome, and by the structure of the uropoda and 

 especially that of the telson. The genus comprises several species, one of 

 which belongs to the fauna of Norway, and will be described below. All the 

 species are, as yet known, fresh-water forms. 



