download pdf

177
the posterior corners acutely produced. Metasome occupying about x
/4 of the
length of the body, epimeral plates of 3rd to 5th segments strongly recurved;
last segment rather produced, terminating in an acute point slightly grooved
dorsally. Antenna? less slender, scarcely attaining half the length of the body,
flagellum about as long as the last peduncular joint, and having its 2 articulations
of nearly equal size. Last pair of legs differing but little in the two sexes.
Opercular plates of only the 2 anterior pairs of pleopoda with air-cavities. Uro-
poda with the outer ramus broadly lanceolate, and comparatively larger in male
than in female. Colour of dorsal face generally a uniformly greyish black; some-
times, however, lighter, and variegated with irregular dark patches, more rarely
black, with the side-plates light yellowish. Length of adult female 14 mm.
Remarks. Of all our Oniscoida, this is perhaps the commonest' and
most widely distributed species. I have taken it rather abundantly around Chri-
stiania, especially in refuse-heaps. At Drobak it is also very common, both in
the town and at some distance from it, beneath stones on the beach. Further-
more, I have taken it at Skien, and at Sauesund, west coast of Norway. In the
latter place it occurred near the shore, just above high-water-mark, beneath decaying
alga3, and in company with Ligia oceanica. According to conservator Storm, it
is also common at Trondhjem, and last summer conservator Sig. Thor collected
it on one of the Lofoten Islands. Finally,
I have received from conservator
Schneider a few specimens of this species taken in Finmark from a Laplanders
turf-hut. The variety marmorata is found occasionally both here in Christiania
and at Drobak together with the typical form, and more rarely also the var.
marginata, in which the dark back is flanked by a broad light yellow border oc-
cupying the side-plates of the mesosome. The animal is rather agile, running
away with considerable speed, when disturbed, to conceal itself.
Distribution. Northern, western and central Europe everywhere, south
Europe less frequent, Iceland, Greenland, North America, Mexico,
Paul, St. Croix and Ascension, Kamtschatka, Cape of Good Hope.
2. Poreellio pictus, Brandt.
(PI. LXXVIII, fig. 1.)
islands St.
Poreellio pictus, Brandt & Ratzebm-g, Medicin. Zoologie, Vol. II, p. 78, PI. 12, fig. 5.
Syn: Poreellio melanocephahts, Koch.
mixtus, Fitch.
Specific Characters. Body oblong oval, and considerably depressed, with the
face rough owing to the presence of small elevated tubercles, less densely crowded than
in P. scaber. Cephalon with the lateral lobes very large and slightly
23 Crustacea.
curved out-