46 



antennae with the inner ramus well developed, though somewhat shorter than the 

 outer. Mandibles comparatively narrow, with the teeth of the masticatory part 

 simple. Maxillse normal. Anterior maxillipeds with each of the 2 outer digitiform 

 lobes carrying a strong, claw-like spine, coarsely denticulate inside. Posterior 

 maxillipeds rather slender. Inner ramus of 2nd to 4th pairs of legs armed on 

 the hind face with oblique rows of rather strong spinules. Last pair of legs in 

 female with the terminal joint spiniferous; those of male comparatively simple, 

 left leg very slender, . right rudimentary or wanting. 



Remarks. This genus was established in the year 1892 by Dr. Giesbrecht, 

 to comprise 2 supposed species from the Mediterranean, s viz., X. agilis and minor. 

 In my opinion, however, the latter species ought to be discarded, being apparently 

 only founded upon immature specimens of the former. The genus is easily 

 distinguished both from Phaenna and Pseudophaenna by the less robust form of 

 body, the structure of the rostral part, and the acutely produced lateral lobes 

 of the last segment of the metasome. Moreover, the 2 strong and coarsely dentate 

 spines on the anterior maxillipeds are rather characteristic, as also the structure 

 of the last pair of legs in both sexes. Two well-defined, though closely allied 

 species, to be described below, belong to the fauna of Norway. 



19. Xanthocalanus borealis, G. 0. Sars. 



(PI. XXXI, XXXII). 



Xanthocalanus borealis, G. 0. Sars. Crustacea of the Norwegian North Polar Expedition, 



p. 49, PL XI. 



Specific Characters. Female. Anterior division of body, seen dorsally, 

 oblong ovaj. in form, greatest width not attaining half the length, anterior extremity 

 narrowly rounded, posterior slightly contracted. Cephalosome evenly vaulted above, 

 .and defined from the 1st pedigerous segment by a faint curved suture. Last 

 segment of metasome completely coalesced with the preceding one, lateral lobes 

 drawn out to acute, posteriorly-pointing lappets reaching in adult specimens beyond 

 the middle of the genital segment. Urosome scarcely exceeding y 4 of the length 

 of the anterior division, genital segment fully as long as the 2 succeeding ones 

 combined. Caudal rami very short, scarcely longer than they are broad, apical 

 setae much elongated, especially the innermost but one, and somewhat divergent. 

 Anterior antennae very slender, when reflexed reaching about to the end of the 

 genital segment. Posterior antennae with the outer ramus but slightly exceeding 

 the inner in length. Spinules on the hind face of the inner ramus in 2nd and 

 3rd pairs of legs regularly disposed in a single oblique row, those in 4th pair 



