34 



tenuated distally, tip obtusely acuminate, and exhibiting on each side a small 

 semilunar notch; antero-lateral corners triangular, defined above by a deep sinus. 

 Carapace of male less compressed, exhibiting, however, a complete series of den- 

 ticles along the middle of the dorsal face ; pseudorostral projection much shorter 

 than in female, with the lower edges serrate; antero-lateral corners blunted. 1st 

 pair of legs about as in L. fulrus; 2nd pair likewise rather similar, though hav- 

 ing the last joint shorter than the 2 preceding ones combined. 3rd pair of legs 

 in male with 3 very largely developed lanceolate appendages of the ischial joint. 

 Uropoda scarcely attaining the length of the last 2 segments combined, rami 

 exceeding in length the basal part, outer ramus much the longer, and carrying 

 9 or 10 ciliated setae, inner ramus with the distal joint gradually tapered to a 

 mucroniform point. Colour pure white. Length of adult female 4 mm., of 

 male 4y 2 mm. 



Remarks. This form is easily distinguishable from the 3 preceding species, 

 not only by its small size and pale colour, but, in the female sex at least, by the 

 comparatively long and attenuated, horizontally extended pseudorostral projection, 

 as also by the different structure of the uropoda. The adult male, too, differs 

 conspicuously from the males of the other species in the presence of a distinct 

 series of denticles along the middle of the dorsal face of the carapace ; moreover, 

 in the 3rd pair of legs there are 3, instead of 2 appendages of the ischial joint. 



Occurrence. I first found this form in the Christiania Fjord, at Dr0bak, 

 and have subsequently met with it also in a few other places of the Norwegian 

 coast, for instance in the Trondhjem Fjord and off the Lofoten Islands. It is a 

 true deep-water form, only occurring in greater depths, from 60 to 400 fathoms. 



Distribution. South of Spitsbergen (Norw. North Atl. Exped.). 



5. Leucon acutirostris, G. 0. Sars. 



(PI. XXVI.) 



Leucon acutirostris, G. O. Sars, Om den aberrante Kvebsdyrgruppe Oumacea og dens iiordiske 



Arter, p. 56. 



Specific Characters. Body in female rather short and thick, with the 

 tail scarcely as long as the anterior division. Carapace about the length of the 

 exposed part of the trunk, dorsal crest only confined to the anterior half; pseudo- 

 rostral projection rather small, horizontal, and terminating in a sharp point, below 

 which the edges for some distance are finely denticulate and setiferous; antero- 

 lateral corners distinctly produced, and defined above by an angular cleft. Adult 

 male much more slender than the female, "with the carapace quite smooth above, 



