483 



Eemarks. The present genus, established by Boeck, differs consi- 



derably from the typical Gammaridse in the structure of the gnathopocla, 

 which are comparatively feeble, and exactly alike in the two sexes. It is more- 

 over distinguished by the small coxal plates, the slender form of the antennae 

 and pereiopoda, and by the great development of the last pair of uropoda. 

 In the recurved dactyli of the 2 posterior pairs of pereiopoda, as also in 

 a few other points, it somewhat resembles the Atylidfe. The genus is not 

 represented beyond the northern Ocean, and comprises 3 Norwegian species, 

 to be described below, one of which is now for the first time established. 



1. Melphidippa spinosa (Goes). 



(PI. 1(39). 

 Gammarus spinosus, Goes, Crust. Amphip. maris Spetsbergia, p. 14, fig. 30. 



Body extremely slender, with the anterior division evenly rounded 

 above. Segments of metasome each produced at the end dorsally to 3 acute 

 posteriorly-pointing spines, having between them small denticles; the 2 ante- 

 rior ones of urosome each with a single spiniform dorsal projection. Cephalon 

 scarcely as long as the first 2 segments of mesosome combined, lateral corners 

 obtusely truncated at the tip. First pair of coxal plates slightly expanded 

 distally, with the anterior corner triangularly produced, terminal edge, as 

 in the succeeding pairs, minutely crenulated and fringed with short setae; 

 5th pair with the anterior lobe deeper than the preceding pair. Epimeral 

 plates of metasome having their posterior edge coarsely and somewhat ir- 

 regularly dentated; those of last segment produced at the lateral corners to a 

 somewhat more projecting tooth. Eyes oval in form, somewhat narrowed 

 above, pigment red, with a whitish coating. Superior antennas nearly equalling 

 the length of the body (without the last pair of uropoda), 2nd joint of the 

 peduncle much longer than the 1st, and having in its outer part several 

 fascicles of slender diverging spines, last joint very small, scarcely attaining 

 Y-i of the length of the 2nd, flagellum nearly 3 times as long as the peduncle, 

 and composed of about 24 articulations, accessory appendage not very large, 

 and only composed of 2 articulations. Inferior antennae somewhat shorter 

 than the superior, last joint of the peduncle not attaining the length of the 

 penultimate one, flagellum about half the length of the peduncle. Anterior 

 gnathopoda with the carpus rather large, forming inferiorly a broad laminar 

 expansion densely setous at the edge, its outer part gradually tapering, pro- 

 podos much shorter than the carpus and greatly constricted at the base 



