535 



eoxal plates somewhat deeper than the corresponding segments, 1st pair con- 

 sideraljly expanded distally, 4tli pair with the posterior expansion angnlar. 

 Last pair of epimeral plates of metasome produced at the lateral corners to 

 a small dentiform projection. Eyes wholly wanting, not even the slightest 

 trace of any pigment being visible in the living animal. Superior antennse 

 somewhat exceeding 'A of the length of the body, and scarcely reaching 

 beyond the peduncle of the inferior ones, flagellum nearly twice the length 

 of tlie peduncle, and composed of 18 — 20 articulations, accessory appendage 

 exceeding half the length of the flagellum, and composed of 10 — 12 articula- 

 tions. Inferior antennae of the usual structure. Gnathopoda rather strong, 

 l)oth pairs having the palm of the propodos defined below by a some- 

 what projecting angle armed witli several strong spines, dactylus of the 

 anterior ones with 4 serrations at the base, that of the posterior with about 

 '.• serrations, occupj-ing the proximal Vs of tlie dactylus. Posterior 

 gnatliopoda in male rather unlike those in female, having the propodos 

 exceedingly large and much dilated at the base, its outer part tapering 

 distalh', palm nearly straight and finely ciliated, terminating in front in 

 an angular, slightly dentated lobe, dactylus enormously developed and much 

 curved, without any trace of serrations. The 3 posterior pairs of pereiopoda 

 rapidly increasing in length, and having the basal joint less expanded than 

 in the other species, and of an oblong form; last pair very much elongated, and 

 rather more strongly built in male than in female, propodal joint carrying small 

 bristles on both edges, dactylus comparatively short. Last pair of uropoda 

 of the usual structure. Telson considerably more elongated in male than in 

 female, cleft very narrow, and extending somewhat beyond the middle, 

 terminal lobes bidentate at the tip, and each carrying a slender apical si)ine. 

 Colour uniformly yellow. Length of adult female 10 mm., of male 11 mm. 

 Maximum length of arctic specimens 20 mm. 



Itemarlis. — This form was first descril)ed Ijy my late father as 

 Gammarus fisxicornis, and was subsequently erroneously identified by Goes 

 with G. pallidus of Sp. Bate. From the latter species it is at once 

 ilistinguished by the absolute want of eyes, and by the very large dorsal 

 ])rojections of the 2 anterior segments of the urosome. The sexual difference 

 in this form is very jtromineutly revealed in the structure of the posterior 

 gnathoj)oda; the last pair of jjereiojioda also are much more strongly built in 

 tlie male than in the female, both characteristics thus strongly recalling the 

 genus Cheirocratm. 



Occurrence. — Off the coast of Finmark this form is not infrequently 

 met with in greater de])tlis, varying from 50 to 200 fathoms. It extends 

 southwards along the Nordland coast, at least to the Throndlijemsfjord, 



