416 



pereiopoda generally very feeble in structure, the 3 posterior pairs more or 

 less elongated and slender, with the basal joint oblong oval in form. Last 

 pair of uropoda scarcely projecting beyond the others, and having the rami 

 lanceolate and edged with small denticles. Telson elongate, tapering distally, 

 outer part more or less deeply incised. 



Remarks. - - The present genus, the type of the family, was established 

 by Kroyer in the year 1845, to include an arctic species E. cuspidatus. It is 

 chiefly distinguished by the peculiar structure of the gnathopoda, which differs 

 considerably from that ^in most other Amphipoda. The genus comprises no 

 less than 5 Norwegian species, to be here described, 3 of which are 

 now for the first time established. Besides, a 6th species has been described 

 by Dr. Hansen as E. Holmii, from the Kara Sea, and the same form was 

 also collected on the Norwegian North Atlantic Expedition, but was at that 

 time erroneously recorded as E. cuspidatus. 



1. Eusirus cuspidatus, Kroyer. 



(PI. 146). 

 Eusirus cus2)idatus, Kr0yev, Nat. Tidsskr. 2 R. p. 501, PI. 7, fig. 1. 



Body comparatively rather robust, though considerably compressed, 

 and having the posterior part of the back distinctly carinated, the carina 

 being produced, in the last 2 segments of mesosome and the first 2 of 

 metasome, to acute, posteriorly-pointing projections. First segment of urosome 

 with a slight dorsal carina in its posterior part. Cephalon scarcely attaining 

 the length of the first 2 segments of mesosome combined, rostral projection 

 short and obtuse, lateral corners rather broad, and slightly bilobate. Anterior 

 pairs of coxal plates fully as deep as the body; 1st pair moderately expanded 

 distally, having the anterior corner evenly rounded, the posterior one divided 

 into 3 small serrations; the 2 succeeding pairs somewhat tapering distally, 

 and having likewise 3 small serrations at the infero-posteal corner; 4th pair 

 nearly twice as broad as the preceding pair, and produced posteriorly, below 

 the emargination, to an angular projection. Last pair of epimeral plates of 

 metasome evenly rounded at the lateral corners, and minutely serrated 

 throughout the considerably arched posterior edge. Eyes rather large, and 

 oval reniform in shape. Superior antennae almost attaining half the length 

 of the body, the first 2 joints of the peduncle about of same length, and both 

 produced at the end to small lappets divided into several obtuse denticles, 

 last joint very short, flagellum about twice the length of the peduncle, and 

 composed of numerous small articulations, without any calceolee, but carrying 



