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the mandibles, in particular, is very different from that in the other Desmosomidw.
The genus comprises as yet but a single species, to be described below.
Echinopleura aeuleata, G. 0. Sars.
(PL LVI.)
Desmosoma aculeatmn, G. 0. Sars, Om en anunial Grnppe af Isopoder. Clir. Vid. Selsk. Forlil.
1863, p. 13.
Specific Characters. Body slender, moniliform, about 4 times as long as
it is broad, anterior division much broader than the posterior,
and oval in form.
Cephalon comparatively large, and very distinctly notched on each side, frontal
part in female broadly truncated, in male narrower and distinctly
insinuated at
the tip, edges of the lateral notches strongly denticulate. Lateral parts of the
4 anterior segments of mesosome with about 6 strong serrations, anterior edge,
except in the 1st segment, with a dense row of minute denticles; 4th segment
abruptly narrowed behind, and firmly connected with the 5th, both together form-
ing an hour-glass-shaped section, about as long as the 3 anterior segments com-
bined. The 2 posterior segments of mesosome deeply constricted at the base, and
gradually widening behind, lateral edges, as in the preceding segment, coarsely
and regularly serrated throughout. Caudal segment oval in form, deeply con-
stricted at the base, lateral edges coarsely denticulate, tip narrowly rounded.
Superior antenme 4-articulate, and carrying a long apical sensory
filament. In-
ferior antennae in female scarcely exceeding V 3 of the length of the body, flagel-
lum shorter than the peduncle, and composed of 8 articulations; those in male
transformed in a similar manner to that in the male of Desmosoma, though not
much tumefied, peduncle without an}' spines. 1st pair of legs rather slender, but
scarcely at all attenuated, basal joint long and narrow, and finely serrated in
front, ischial joint exhibiting outside a small spiniforin projection, carpus
with 4
slender spines inside, propodos about the same length, but much narrower, simple,
cylindric, dactylus rather strong. The 3 succeeding pairs of legs scarcely longer
than the 1st, and of a very similar structure, though having the dactylus narrower.
The 3 posterior pairs of legs extremely slender, with the outer joints but slightly
expanded, and only provided with a very restricted number of spines, dactylus
slender, styliform. Uropoda comparatively small, distal joint 3 times as long as
the proximal one, and carrying only 4 or 5 bristles. Colour greyish white.
Length of adult female 2y2 mm., of male V/'-> mm.
Remarks. This form was described by the present author as early as in
the year 1863, as a species of the genus Desmosoma. Its outward appearance is