download pdf

59
1. >ga psora (Lin.).
(PI. XXIV.)
Oniscus psora, Linne, Fauna svecica, ed. II, 17H1.
Syn: ^Ega emaryinata, Leach.
Specific Characters. Body rather broad,
oval in form, about twice as
long as it is broad, with the dorsal face but slightly vaulted, and very smooth and
polished; transverse lines of the 4 posterior pedigerous segments
indistinct. Ce-
phalon with the front slightly produced in the middle. Coxal plates of moderate
size. Metasome about half the length of the mesosome, epimera well- developed
and pointed. Terminal segment triangular, pointed at the tip, dorsal face smooth.
Eyes subreniform, separated in the middle by a distinct, though
rather small
interspace. Superior antenna? with the first 2 peduncular joints rather broad,
the 2nd being produced at the end anteriorly to a hood-like projection curving
over the succeeding joint, liagellum about half the length of the peduncle. In-
ferior antenna? nearly twice as long as the superior, with the rlagellum somewhat
longer than the peduncle. 1st pair of legs with only 2 blunt spines at the end
of the meral joint inside, the 2 succeeding pairs with a row of from 7 to 8 si-
milar spines on the same joint; the 4 posterior pairs with the outer part densely
clothed with short spines. Uropoda with the inner plate deeply emarginated
near the end, outside, outer plate oblong, with about 12 short spines along tin-
exterior edge. Colour light reddish brown. Length of adult animal reaching
to 50 mm.
Ji'emarJcs. This is the species first recorded, and may accordingly be
regarded as the type of the genus. It is easily recognizable by the rather broad,
oval body, the distinctly separated eyes, and more especially by the form of the
terminal segment of the metasome, and the deep emargination occurring on the
inner plate of the uropoda, outside the tip. The name emarginata proposed by
Leach, was, indeed,
derived from this last character.
Occurrence. This species occurs rather frequently along the whole coast
of Norway, from the Christiania Fjord to Vadso, being more generally found on
the cod, but occasionally also on other kinds of fishes, for instance the haddock,
the ling, the halibut and the shark. It is also not infrequently taken up in the
dredge, but, as a rule, only young specimens are caught
in this manner.
Distribution. British Isles (Sp. Bate), Kattegat (Meinert),
North Sea
(Metzger), Ireland (Edwards), Spitsbergen (Miers), Greenland (Liitken), Atlantic
coast of North America (Harger).