30 
antennae in female with the distal joint well defined. 1st pair of legs slender, 
with the terminal part much longer than the basal 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 Kroyer 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. Leueon nasieus, Kroyer. 
(PI. XXI, XXII.) 
Ouma nasica, Kroyer, Nat. Tidsskr. Vol. Ill, p. 524, PI. VI, figs. 31—33. 
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 setae 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 
