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137
2. Ilyarachna hirticeps,
(PI. LX.)
G. 0. Sars.
ll//arachna hirticeps, G. O. Sars, Nye Dybvandscrustaceer fra Lofoten. Chr. Vid. Selsk. Porhdl.
1869, p. 167.
Specific Characters. Body of a similar appearance to that in the type
species, but more than twice as large, and somewhat more robust. Cephalon
very broad, with the dorsal face strongly vaulted, and densely clothed with short
stout bristles. Anterior edge of the first 4 segments of mesosome very distinctly
elevated, and minutely crenulated throughout; lateral paits of 1st segment imper-
fectly developed. The 3 posterior segments of mesosome combined about the
length of the preceding part of the body ; the anterior segment evenly emarginated
behind. Caudal segment of a similar form to that in J. longicornis. Superior
antennae comparatively short, not nearly reaching to the middle of the penultimate
peduncular joint of the inferior ones, basal joint armed along the inner edge with
scattered denticles, flagellum, in female, not attaining the length
of the last 2
peduncular joints combined. Inferior antennae scarcely twice as long as the body,
penultimate joint of the peduncle armed inside with 7 strong spines. Legs, on
the whole, resembling in structure those in the type species, though
the 3rd and
4th pairs are somewhat less elongated, and the natatory legs more densely fringed
with seta?. Uropoda with the proximal joint rather large, and somewhat widening
distally, marginal seta? about 20 in number, distal joint very narrow, linear.
Colour whitish grey. Length of adult female 772 mm.
Eemarks. This species is nearly allied to the preceding one, but of very
much larger size, and, moreover, easily distinguishable by the dense setous clothing
of the dorsal face of the cephalon, and by the strongly elevated and finely cre-
nulated anterior edges of the anterior segments. Several other minor differences
may also be shown to exist, on a closer comparison of the several appendages in
the two species.
Occurrence. This species would seem to be a true arctic form, having
not, as yet, been found south of the Lofoten Islands, whereas it is not unfrequently
met with on the Finmark coast as far as Vadso.
Distribution. Several stations of the Norwegian North Atlantic Expedition
(the present author), Greenland (Hansen).
18 Crustacea.