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G.O. Sars, 1865

Description
Body slender and highly compressed, with the tail about the length of the anterior division.
Carapace in female somewhat exceeding the length of the exposed part of the trunk, dorsal crest very fully developed, extending to the hind edge; pseudorostral projection considerably produced, horizontal, attenuated 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 denticles along the middle of the dorsal face; pseudorostral projection much shorter shall in female, with the lower edges serrate; antero-lateral corners blunted. First pair of legs about as in Leucon fulvus. Second pair likewise rather similar, though having the last joint shorter than the two preceding ones combined. Third pair of legs in male with three very largely developed lanceolate appendages of the ischial joint.
Uropods scarcely attaining the length of the last two segments combined, rami exceeding in length the basal part, outer ramus much the longer, and carrying nine or ten ciliated setae, inner ramus with the distal joint gradually tapered to a mucroniform point.
This form is easily distinguishable from the three 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 uropods. 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 third pair of legs there are three, instead of two appendages of the ischial joint.

Size
Length of adult female 4 mm, male 4.5 mm.

Colour
Pure white.

Ecology
True deep-water form, only occurring in greater depths.

Depth range
Down from 120 to 750 m.

Distribution in the North Sea
Northern North Sea, Skagerrak.

World distribution
South of Spitzbergen

[After Jones, 1976]

Leucon pallidus