NO. 6.] ACCOUNT OF THE SPECIES. 49 



somewhat different. Dr. Giesbrecht records 2 species of this genus, both from 

 the Mediterranean, and I have myself found another species off the Norwegian 

 coast. From the Nansen Expedition a single, somewhat defective female 

 specimen of the latter species is derived, to be described below. 



5. Xanthocalanus borealis, n. sp. 

 (PI. XI). 



Specific Characters. 9- Anterior division of body rather tumid and 

 greatly vaulted above, regularly oval in form, greatest width almost 

 attaining half the length, front narrowly rounded, last segment imperfectly 

 defined, with the lateral parts angularly produced behind. Tail scarcely 

 attaining Vs of the length of the anterior division, genital segment about the 

 length of the 2 succeeding segments combined, last segment very small, 

 caudal rami short, slightly divergent. Anterior antennae exceeding in length 

 the anterior division of the body, and 24-articuIate. Posterior antennae with 

 the outer ramus considerably longer than the inner. Anterior maxillipeds 

 with the outermost spine very strong and coarsely denticulate, apical sensory 

 appendages comparatively small, 8 in number. Posterior maxillipeds with 

 the terminal part comparatively short, and not recurved. Last pair of legs 

 biarticulate, distal joint constricted in the middle, and carrying at the tip 3 

 strong, denticulated spines of about equal size. Length of adult female 

 4 mm. 



Remarks. This form differs at once from the 2 Mediterranean species 

 described by Dr. Giesbrecht, in its much larger size and more robust form 

 of body. In the structure of the last pair of legs, it more resembles the 

 smaller species, X. minor, than the larger X. agilis, the length of which 

 according to Dr. Giesbrecht, is only 2'40 mm. 



Description of the Female. 



The length of the one specimen in the collection, which is an adult female, 

 is 4 mm., or nearly twice that of the larger Mediterranean species. 



The general form of the body (see figs. 1 & 2) is rather robust, with the 

 anterior division considerably tumefied, and greatly vaulted dorsally. Seen 

 from above (fig. 1), this division exhibits a rather regular oval form, with the 



