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24
dannet til en kraftig tilspidset og svagt krummet Endeklo.
Begge disse Fodpar er temmelig rigeligt besatte med korte
Borster.
Gjellernes Antal er (se Fig. 21) 5 paa hver Side,
svarende til de 5 Par Fodder. I sin Bygning og Udseende
viser de intet usædvanligt.
Bagkroppens Svouimevedhæng (Fig. 24–25) er kraftigt
udviklede og rettede noget skraat udad til Siderne, saa at
deres ydre Del viser sig. naar Dyret sees -ovenfra (Fig. 1),
ragende frem til hver Side. De bestaar af en særdeles tyk
og muskuløs Roddel eller Stamme, til hvis Ende er
ind-leddet 2 uligestore Grener. Den ydre af disse er storst,
dannende en langs Kanterne tæt borstebesat, lancetformig
Plade af Stammens dobbelte Længde. Den indre Gren er
neppe mere end halvt saa lang, paa 1ste Par uleddet, paa
de øvrige bestaaende af to tydelige Segmenter. Paa de to
forreste Par er denne Gren noget ulige lios begge Kjøn.
Hos Hunnerne er den paa 1ste Par (Fig. 24) af elliptisk
Form. men noget vreden, saa at den vanskeligt kan
udbredes i samme Plan. Hos Hannerne er den (Fig. 20)
derimod tydelig indknebet paa Midten og noget udvidet i
liver Ende, samt lier forsynet med lange og stive, ucilierede
Borster. Paa 2det Par er denne Gren hos Hunnerne (Fig.
25) fuldkommen af samme Udseende som paa de følgende,
bestaaende af 2 med hinanden knæformigt forbundne
Segmenter, hvoraf det yderste er længst og smalt lancetformigt.
Hos Hannerne har den (Fig. 27) et temmelig afvigende
Udseende. Den bestaar vistnok ogsaa her af 2 Segmenter,
men det yderste er her tvedelt eller gaar ud i to ulige
lange, med stærke Borster besatte l apper.
Det midterste Halevedhæng (Fig. 28), der egentlig
forestiller Bagkroppens sidste Segment, er af. smal,
lancet-dannet Form og oventil langs ad Midten noget udhulet,
med to stumpe Sidekjøler, hvoraf enhver bag Midten hæver
sig til 2 skarpe tornformige Fortsatser. Enden er udtrukket
til en triangulær Spids, og til liver Side af denne er
ind-leddet en kort Torn. Langs ad Sidekanterne af Vedhænget
tindes desuden en tæt Rad af Fjærborster.
De ydre Halevedhæng (Fig. 28), der sammen med
det midterste danner den saakaldte Halevifte, bestaar af
en kort. paa Ydersiden i en stærk tornformig Fortsats
udgaaende Roddel og to omtrent lige lange pladeformige
Grene. Den ydre af disse er noget bredere end den indre
og liar den ydre Kant glat samt løbende bagtil ud i en
stærk Torn, hvorfra en tydelig Sutur strækker sig paaskraa
tværsover Pladens ydre Del. Kanterne er forøvrigt paa
begge Grener forsynede med en regelmæssig Rad af korte
Fjærbørster. Den ovre Flade er paa den ydre Gren
forsynet med to. paa den indre med en enkelt stump Længdekjøl.
Farren er i levende Tilstand overalt rodlig brun. som
larger than the 5th. The last segment is transformed into
a strong, pointed, and slightly curved terminal claw. Both
these pairs of legs are rather closely beset with short
bristles.
The branchiae (see tig. 21) are 5 in number on either
side, corresponding to the 5 pairs of feet. In their structure
and appearance they exhibit nothing uncommon.
The natatory appendages of the abdomen (tigs. 24.
25) are powerfully developed and directed somewhat obliquely
sideways; hence, their exterior part appears, when the
animal is viewed from above (fig. 1). to project out from
either side. They consist of an exceedingly thick and
muscular basal portion, or stem, to the end of which are
jointed in 2 branches of unequal size. The outer branch is
the larger, constituting a lanceolate plate, twice the length
of the stem, and thickly beset with bristles along the edges.
The inner branch is scarcely half as long; on the 1st pair
it has no articulations, on the others it consists of two
distinct segments. On the 2 foremost pairs, this branch
differs somewhat in the 2 sexes. In the females, it has on
the 1 st pair (fig. 24) an elliptic form, but is somewhat twisted,
so as with difficulty to admit of being spread out in the
same plane. In the males, on the other hand, it is (fig.
20) distinctly constricted in the middle, and somewhat
expanded at either extremity, as also furnished with long and
stiff unciliated bristles. On the 2nd pair, this branch is
in the females (fig. 25) of precisely the same appearance
as on those succeeding it, consisting as it does of 2
connected geniculate segments, of which the outer one is the
longer, and narrow lanceolate. In the males, it exhibits
(fig. 27) a rather different appearance. True, it consists
of 2 segments; but the outer one is bipartite, or protends
in 2 lobes of unequal length, beset with strong bristles.
The telson (fig. 28), that strictly represents the last
segment of the abdomen, is slender, lanceolate in form,
and somewhat hollowed out above, along the middle part,
with two obtuse lateral carinæ, each of which, posterior to
the middle, rises as an acute spiniform prölation. The
extremity is drawn out to a sharp triangular point, on
either side of which is jointed in a short spine. Extending
along the lateral borders of the appendage, occur moreover
a close-set series of plumose bristles.
The exterior caudal appendices or uropoda (fig. 29).
which, together with the telson. form the so-called caudal
fan, consist of a short basal part, produced on the outer
side as a strong spiniform probation, and of two lamellar
branches about equal ill length. The outer of these
branches is somewhat broader than the inner, with the
exterior margin smooth and projecting posteriorly as a
powerful spine, whence a distinct suture passes obliquely
straight across the outer portion of the plate. For the
rest, the borders of both branches are furnished with a
regular series of short plumose bristles. On the upper
surface of the outer branch occur two obtuse, longitudinal
carinæ, on that of the inner a single one.
Colour in a living state everywhere reddish-brown, as
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