32 



the trunk, dorsal crest extending to the hind edge, frontal lobe moreover armed 

 on each side with 3 small denticles, 2 successive subdorsal, and one lateral, 

 pseudorostral projection much shorter than in L. nasicus, horizontal and obtusely 

 truncated at the tip, its terminal edges being cut off into 4 denticles, infero-lateral 

 corners but slightly produced. Adult male much more slender than the female, 

 and having the carapace smooth, with only 2 small successive denticles close to 

 the end of the frontal lobe; pseudorostral projection transversely truncated, with 

 only 2 denticles on the terminal edges below, infero-lateral corners obtusangular. 

 Superior antennae smaller than in the type species, with the last joint of the 

 peduncle shorter than the 2nd. 1st pair of legs comparatively feebler in structure, 

 with the penultimate joint much shorter than the antepenultimate one. 2nd pair 

 of legs with the last joint about the length of the antepenultimate one, and 

 armed with several rather unequal spines, which are not ciliated. 3rd pair of legs 

 in male with 2 subequal, narrow lanceolate appendages of the ischial joint. Uro- 

 poda with the rami subequal in length, and somewhat longer than the basal part, 

 the inner one without any ciliated setae outside, its distal joint not nearly at- 

 taining half the length of the proximal one, and carrying about 6 ciliated spines 

 gradually increasing in length distally ; outer ramus with only a very limited 

 number of setse. Colour whitish, with a faint yellowish tinge. Length of adult 

 female 6 mm., of male about the same. 



Remarks. This form, first described by Prof. Lilljeborg, is easily distin- 

 guishable from the type species by its much shorter and more robust body, the 

 fuller development of the dorsal crest of the carapace, and the shorter pseudo- 

 rostral projection. In the structure of the several appendages also, well-marked 

 differences are found to exist. 



Occurrence. I have met with this form, though nowhere in any abun- 

 dance, in several localities of the Norwegian coast, from the Christiania Fjord to 

 the Lofoten Islands, in depths varying from 10 to 50 fathoms. 



Distribution. Kattegat (Lilljeborg), Greenland (Hansen). 



3. Leucon fulvus, G. 0. Sars. 



(PI. XXIV.) 



Leucon fulvus, G. O. Sars, Om den aberrante Krebsdyrgruppe Cumacea og dens nordiske Arter. 



Chr. Vid. Selsk. Forh. 1864, p. 55. 



Specific Characters. Body rather slender, especially in the male, with the 

 tail unusually narrow and scarcely as long as the anterior division. Carapace 

 in female about the length of the exposed part of the trunk, dorsal crest well 



