30 



antennae in female with the distal joint well defined. 1st pair of legs slender, 

 with the terminal part much longer than the hasal joint, last joint compressed 

 and densely clothed with slender curved spines; 2nd pair rather robust, last joint 

 armed with diverging spines ; the succeeding pairs comparatively short, and densely 

 setiferous; 3rd pair in male with 2 or 3 peculiar appendages attached to the 

 ischial joint inside. Uropoda with the rami scarcely differing in size. 



Remarks. This genus was established by Kr0yer as early as in the year 

 1846; but he also comprised within it species of the other 2 genera belonging 

 to this family. In the restriction here adopted, the genus is easily recognized, 

 at any rate in the female sex, by the crested carapace, the distinctly prominent 

 pseudorostral projection, and the angular incision below the latter. The genus 

 comprises, as yet, no less than 11 species, 5 of which belong to the fauna of 

 Norway, and will be described below. 



l. Leucon nasicus, Kroyer. 



(PI. XXI, XXII.) 



Ouma nasica, Kroyer, Nat. Tidsskr. Vol. Ill, p. 524, PI. VI, tigs. 3133. 

 Syn: Leuconopsis ensifer, Walker (male). 



Specific Characters. Body exceedingly slender and elongated, with the 

 tail very fully developed, and longer than the anterior division. Carapace in 

 female shorter than the exposed part of the trunk, dorsal crest extending beyond 

 the middle, and reappearing for some distance also in the hindmost part, pseudo- 

 rostral projection exceedingly prominent and somewhat upturned, obliquely truncate 

 at the tip, with the ., terminal edges very minutely denticulate and setiferous, in- 

 fero-lateral corners triangularly produced, and defined above by a deep angular 

 cleft. Carapace in male comparatively larger and less compressed, without any 

 trace of a dorsal crest, pseudorostral projection shorter and almost transversely 

 truncated at the tip, infero-lateral corners blunted, subrostral sinus obsolete. 

 Superior antennae with the last joint of the peduncle fully as long as the 2nd, 

 and conically tapered. 1st pair of legs rather elongated, and but slightly attenu- 

 ated, with numerous plumose setse both on the basal and terminal parts, penulti- 

 mate joint almost as long as the antepenultimate, and twice the length of the terminal 

 joint; 2nd pair with the last joint shorter than the antepenultimate one, and car- 

 rying about 9 diverging ciliated spines. 3rd pair in male with 2 very conspicuous, 

 ensiform appendages of somewhat unequal size, originating from inside the ischial 

 joint. Uropoda about the length of the last 2 segments combined, and rather 

 robust, rami of about equal length, the inner one with numerous unequal spinules 



