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and the basal spines are very much reduced. Dorsally-dis tally un the second to the eighth
joints there is a cluster of rather long, fine hairs. Endopodite: The end joint is rather
decidedly curved and is somewhat more than half the length of the second joint; it can be folded
back against a corresponding furrow on the second joint. The lirst joint has no bristles at all.
The second joint has (always?) three bristles ventrally at about two-thirds or three-quarters
along the joint. The end joint has a single bristle proximally on the outside; this bristle is of
about uniform thickness and is rounded distally.
Man dible: —
Female: — This is relatively short, but is very powerfully built, vvitli its joints
decidedly flattened at the sides. The proportions between the joints are about the same in all
the species investigated by me and are illustrated by the following figures (from measurements
carried out on a specimen of A. norvegica, $):
1 Pr. “; II Pr. I End. II End. 111 End. ‘.
Pr o to pod i te: Coxale: This has no bristles. The endite issues from, or perhaps it would
be more correct to say forms basally, a chitinous list, which extends transversely across the joint;
cf. G. O. SARS, 1887, pl. IV, fig. 4. The scythe-shaped process is uniformly and moderately
strongly curved in two planes, partly upwards, partly inwards, and is, in addition, slightly
twisted so that its medial side is turned somewhat upwards; it is thus turned towards the mouth,
in which I often found it inserted (already observed by G. W. MÜLLER; cf. 1894, p. 46). On the
distal part of its ventral edge there is always a more or less strongly developed spine, pointing
proximally, characterized by the faet. that it is continued by a low ridge, in most cases rather
short, on the lateral side of the process. This ridge forms a curve which is concave proximally
and is furnished, like the spine, with a close series of rather short, fine, stifï spines, pointing
proximally. Proximally of this spine there is along the ventral edge of the process a number
- in most cases rather small — of protubérances or spines; these are most frequently somewhat
different in number and type in different species; within the species they are certainly not
constant, but their variation is not so great that they cannot to some extent serve as a character
for the species; I often found them rather strongly worn, which may, of course, modify their
appearance considerably. From some of these spines a series of low protubérances runs in
a dorso-proximal direction on the lateral side of the process; in a number of species these
protubérances are rather numerous, in others they are more or less sparse; in addition they are
also subject to some variation within the species. Distally of the middle the dorsal edge is often
serrated along, in most cases, a rather short part; the teeth vary in size, in some species they
are even almost completely reduced. The dorsal edge is, in addition, distinguished by a single
bristle, in most cases rather long, which is situated almost opposite or somewhat distally of the
above-mentioned proximally pointing spine on the ventral edge of the process. On a great part of
the surface of the process there are numerous striations, generally speaking parallel to each other,
of which the distal ones at least are furnished with close, extremely short and fine hairs pointing
distally; these hairs are scarcely perceptible even with very strong magnification (Reichert’s
oc. 4, Leitz’s immers. p,). Similar striations, running across the process in distally concave
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