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Crustacea [n.d.]
Genus Gammarus
Body 13-jointed exclusive of the head, and including the 3-jointed tail; antennae
with the last joint composed of numerous minute ones, superiors as long or longer
than the inferiors, 4=jointed, penultimate joint with a ceta at the apex, inferiors
5=jointed; feet 14, the two anterior pairs monodactyle, subequal, hands oval, 3d and
4th pairs smallest; tail with small fasciculate spines above and bifid
ones at tip.
Species
fasciatus, Say. Body whitish translucent, with obsolete greenish bands;
eyes uniform, situated at the outer base of the antenna; terminal
joint of the superior antennae with about 30 articulations.
minus, Eyes periform; superior antennae longer than the inferior
mucronatus Eyes irregularly reinform blackish; antennae subequal;
8th, 9th & 10th segments of the body mucronate above.
appendiculatus, Say. Caudal segments and three terminal segments of the
body dentate on their posterior edges; feet in one sex, 2d pair
didactyle.
Asellus - Geoff.
Tail one large segment; caudal appendages exserted, bifid, inserted near the
middle of the hind margin; exterior branchial valves rounded attached
by the base; tarsi simple; eyes minute; antennae 4, setacious, the
last segment many=jointed.
Species
Communis, Say. Body oblong-oval, furnished with short rigid hairs;
interior antennae equal to the peduncle of the exterior ones;
caudal appendages peduncle depressed.
lineatus, Say. Body oblong: interior antennae much shorter than
the peduncle of the exteriors; caudal appendages, preduncle
cylindrical.
Philoscia - Latr.
Caudal styles 4, simple, salient, lateral ones biarticulate;
antennae, exteriors 8=jointed, interiors obsolete; tail abruptly narrower than the body,
Species
vittata, Say. Fiscous, glabrous, margin two broad vittae cinereous
spinosa, Say. Brown, oblong=oval, with numerous spines above; feet
armed with short setae beneath.
Oniscus
Caudal styles 4, lateral ones biarticulate, intermediate ones concealed by the
terminal segment of the tail; antennae exteriors 8=jointed, interiors
obsolete; tail not abruptly narrower than the body.
Species
affinis, Say. Head and anterior segments of the body seabrous; tail glabrous,
terminal segment attenuated, attaining the tip of the inferior styles;
and the middle of the last joint of the exterior ones.
Porcellio - Latr.
Caudal styles 4, lateral ones biarticulate, intermediate ones concealed by the
terminal segment of the tail; antennae exteriors 7=jointed interiors obsolete;
tail not abruptly narrower then the body .
Species
Spinicornis, Say - Body seabrous; antennae, 3d joint with a muricate
carina above.

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