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Tribe 2.
FLABELLIFERA
Remark*. It is not easy to give any exhaustive diagnosis of this tribe,
as it comprises Isopods of extremely different structure. The only essential cha-
racter common to all the forms, is the relation of the uropoda. which arc not, as
in the preceding tribe, terminal, but lateral, and arranged
to form, with the last segment of the metasome, a caudal fan,
in such a manner as
similar to that
found in some of the higher Crustacea, the shrimps and lobsters. As to the
pleopoda, they exhibit more generally the character of true swimming organs,
though at the same time they may also serve for respiration, and it is only in ex-
ceptional instances that the latter function is exclusively devoted to them. By far the
greater number of the forms seem to lead a parasitic, or at least semi-parasitic exi-
stence, and for this reason, the oral parts are often found to be peculiarly modified,
and, moreover, a number of the legs, in some cases all of them, to assume a more or
less pronouncedly prehensile character. The tribe includes 6 very distinct families,
viz., AntfmridoG, Gnatliiidos, Cymothoidw, Serolidce, Sphcpromidcv
and Limnonidos ;
but of these, the 3rd has generally been again subdivided into 6 families, viz.,
^Eyidce, Cirolanidce, Corallanidce, Alcironidce, Barybrotidm and CymoihoidcB, thereby
increasing
the number of families to no less than 1 1 in all. Five of these families
are represented in the fauna of Norway, and will be here treated of.
Fam. 1. Anthuridae.
Characters. Body long and slender, subcylindric in form,
and rather flex-
ible. Head comparatively small. Segments of mesosome all well defined, and