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peculiar structure of the 4 anterior pairs of legs. The family comprises as yet
3 genera, viz., Arcturus, Astacilla and Arctnrclla, the last 2 of which are repre-
sented in the fauna of Norway, and will he treated of helow.
Gen. 1. AStacilla, Cordiner, 1795.
: Syn Lcacid,
Johnston.
Generic Characters. Body extremely slender, suhcyliudric in form, with
the middle segment of mesosome very much elongated, heing in male narrow cy-
lindric, in female somewhat thicker, and carrying heneath it the incubatory pouch.
The 3 posterior segments of mesosome short and very movably articulated, so as
to allow the anterior part of the body to be bent dorsally at right angles
to the
posterior. Metasome with only a single segment distinctly separated in front of
the terminal one, which is conically produced behind, and exhibits at the base
on each side a small projecting lappet, really indicating the presence of an-
other imperfectly defined segment. Eyes large and prominent, lateral. Superior
antenna; with the tlagellum more fully developed in male than in female, and in
both sexes carrying a number of delicate olfactory filaments arranged along the
outer edge. Inferior antenme very much elongated, though having the flagellum
extremely short, and only composed of 3 articulations finely denticulated inside,
the last terminating in a small spine. Maxillipeds with the palp well developed.
5-articulate, epignath comparatively small, basal part in female produced in a thin
ciliated plate extending posteriorly. 1st pair of legs densely setous, proximal
part of dactylar joint lamellarly expanded; the 3 succeeding pairs very slender,
and fringed with a double row of long seta?, dactylus obsolete. The 3 posterior
pairs of legs smooth, dactylus strong, bidentate at the tip. Uropnda with the ter-
minal piece triangularly pointed, secondary lamella very small, setous at the tip.
Incubatory pouch only formed by a single pair af elliptical valvular lamella-
issuing from the middle segment
of mesosome.
Remarks. As stated by the Rev. Mr. Stebbing, the generic name Asta-
cilla, which has generally been attributed to Fleming, was in fact proposed at a
much earlier date (1795) by the Rev. Charles Cordiner to designate a species of
the present genus. The name Leacla proposed by Johnston in 1825, and used
by some subsequent authors, was merely abandoned, because a very similar name,
that of. Leachia, had been previously applied to a genus of Cephalopods. In any case,
the name Astacilla should be given the precedence, as it is still older than the name