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length, without any distinctly defined squamiform appendage. Oral parts nearly
as in lanira. Legs comparatively short and of uniform structure, the 1st pair
not being prehensile in either sex, dactylar joint 3-unguiculate. Middle piece of
male operculum considerably expanded at the end. Uropoda extremely small, bi-
ramous, rami very short, nodiform. Male smaller than female.
Remarks. This genus, established by Leach in the year 1813, is chiefly
distinguished by the short and flat body, the very small superior
antejmre and
uropoda, and the uniform structure of the legs. It comprises as yet about 7
species, only one of which belongs to the fauna of Norway.
laera marina (Fabr.).
(PI. XLIII.)
Omscus marinns, O. Fabvicius, Fauna Gronlandic-a, p. 252.
: Syn laera
albifrons, Leach.
Eroyeri, Zaddacli.
laltlca, Fr. Miiller.
copiosa, Stimpson.
nil-alls, Kroyer.
Specific Characters. Pody oval in form, scarcely more than twice as long
as it is broad, in male somewhat shorter and stouter than in female, and slightly
widening behind, lateral edges of the segments in both sexes fringed
with rather
short and simple hair-like bristles. Cephalon more than twice as broad as it is
long, lateral expansions obliquely truncated, frontal edge slightly Insinuate, obtusely
produced in the middle. Caudal segment semicircular in shape, comparatively
larger and broader in male than in female, apical notch not very deep. Eyes of
moderate size, rounded oval in form. Superior antenna? reaching but little beyond
the antepenultimate peduncular joint of the inferior ones, flagellum very small, bi-
nrticulate. Inferior antennae about the length of the body, not including the cau-
dal segment, outer appendage of the peduncle replaced by a simple spine, fla-
gellum fully twice as long as the peduncle. Legs but slightly increasing in length
posteriorly, one of the 3 dactylar claws rather small, and somewhat removed from
the tip. the other 2 strongly curved. Female operculum semicircular; middle
piece of male operculum forming at the end, on each side, a rather large expan-
sion terminating in a hook-like, anteriorly-curving point. Uropoda projecting
somewhat beyond the apical notch of the caudal segment, both rami well defined,
though very small, and tipped by a fascicle of bristles, the inner one about half
the length of the basal part, the outer considerably smaller. Body
more or less
thickly dotted with dark brown, sometimes uniformly blackish or variegated with
large whitish patches. Length of adult female 4 mm., of male 3 mm.