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17
viser en meget ujevn Overflade, idet saavel Rygskjoldet som
Ba gkropssegmen terne er tydeligt skulpterede dels med
uregelmæssige knudrede Forhoininger, dels med skarpt
markerede langsgaaende Kjoler, der paa visse Steder hæver sig
i Form af hoie, sammentrykte tornformige Fortsatser.
Nogen tydelig Haarbesætning er kun at se langs de
frie Kanter af Rygskjoldet og Bagkropssegmenterne, medens
selve Rygfladen er paa det nærmeste ganske nogen.
Rygskjoldet (se Fig. 1 og 2), der omtrent indtager
’/s af Totallængden, er oventil stærkt hvælvet og kun i sin
allerforreste Del noget nedtrykt. Seet fra Rygsiden (Fig. 1)
er det næsten overalt af ens Brede, seet i Profil (Fig. 2)
viser det sig derimod fortil betydelig smalere end bagtil,
idet de nedre frie Kanter er fortil stærkt opstigende, medens
de bag Midten danner en stærk bueformig Bøining nedad.
Rygskjoldets Hoide er paa dette Sted neppe mindre end
Breden.
Som ovenfor anført, er Rygskjoldets Overflade meget
ujevn. Man bemærker saaledes 3 meget skarpt markerede
Længdekjøler, der fra den bagre Rand strækker sig forover,
en i Midten og en paa liver Side. Den midterste eller
dorsale Kjol. der er tydelig i hele Rygskjoldets Længde,
gaar ud i 3 særdeles store, sammentrykte, fortilkrumniede
tornformige Fortsatser, alle omtrent af ens Udseende og
skilte ved lige Mellemrum. Den bagerste af disse, der
ial-mindeliglied er lidt mindre end de øvrige 2, staar i kort
Afstand fra Rygskjoldets bagre Rand. den forreste noget
bag Roden af Pandehornet. Sidekjolerne er bagtil temmelig
låve, men hæver sig foran Midten til 2 lignende, dog noget
mindre, skjævt udad og fortil rettede Torner, hvoraf den
bagerste omtrent staar i samme Tværlinie som den midterste
af de dorsale Fortsatser. Længere fortil taber disse
Sidekjoler sig ganske, og Rygskjoldet viser her et noget
fordybet Parti, der udad begrændses af en særdeles stor
triangulært tilspidset og noget skraat udadrettet, horizontal
Fortsats, der. naar Rygskjoldet sees ovenfra (Fig. 1)
indtager dettes forreste Sidehjørner. Disse Fortsatser, der,
skjøndt langt mindre udviklede, ogsaa forefindes hos de øvrige
Crangonider. synes at svare til de saakaldte
Branchiostegal-torner hos andre Macrurer. Lige nedenunder de omtalte
Fortsatser sees et meget lidet tandformigt Fremspring, som
er Ptprygostomialtornen.
Pandehornet viser et fra de øvrige bekjendte
Crangonider temmelig afvigende Udseende. Det er forholdsvis af
ikke ubetydelig Størrelse, ved Roden bredt og fladtrykt,
men derpaa pludselig stærkt sammentrykt fra Siderne og
oxeformigt udvidet, dannende nedentil en i Kanterne tæt
børstebesat vertikal Plade. Selve Enden af Pandehornet
er udtrukket i en lang og skarp, skraat opadrettet,
lancet-formig Spids, der rækker betydelig udover 1ste Par Foleres
Basalled, og giver Dyret, seet fra Siden (Fig. 2) et ganske
eget Pliysiognonii.
Den norske Nordliavsexpedition. G. O. Sars: Crustacea.
exhibit an exceedingly uneven surface, both the carapax
and the abdominal segments being distinctly sculptured,
partly with rough, irregularly disposed prominences and
partly with sharply marked longitudinal cnrinæ, which, in
places, rise as high, compressed, spiniform projections.
Any distinct covering of hair cannot be detected save
along the free margins of the carapax and the abdominal
segments, whereas the dorsal surface itself is well-nigh
wholly naked.
The carapax (see figs. 1. 2). which occupies about
one-third of the total length, is above exceedingly arcuate,
its most anterior portion only being slightly depressed.
Viewed from the dorsal side (fig. 1), it appears almost
everywhere of equal breadth; seen iu profile (fig. 2), on the
other hand, it is much narrower anteriorly than posteriorly,
the inferior free margins ascending considerably throughout
the anterior part, whereas, behind the middle division, they
form an exceedingly arcuate descending curvature. The height
of the carapax is here about the same as the breadth.
As stated above, the surface of the carapax is very
uneven. Thus, it exhibits 3 very sharply marked longitudinal
carinas, extending forward from the posterior margin, one
in the middle and one on either side. The median or
dorsal carina, distinct throughout the whole length of the
carapax. rises into 3 exceedingly large, compressed,
anteriorly curved, spiniform processes, all well-nigh uniform in
appearance and separated by equal spaces. The
binder-most of these, which, as a rule, is somewhat smaller than
the other 2. is placed at a short distance from the posterior
margin of the carapax, the most anterior a trifle behind
the basis of the rostrum. The lateral carinæ are
posteriorly rather low, but, in front of the middle part, rise as
2 similar, but somewhat smaller, spines, pointing obliquely
outward and forward, of which the more posterior about
occupies the same transverse line as the median of the
dorsal processes. Farther forward these lateral carinæ
disappear altogether, and the carapax exhibits here a somewhat
depressed area, which, exteriorly, is bouuded by an extremely
large, triangular-acute, horizontal projection, pointing
somewhat obliquely outward, which, when the carapax is seen
from above, occupies its antero-lateral angles (fig. 1). These
processes, though much less developed, also occur in the other
Crangonidians, corresponding apparently to the so-called
branchiostegal spines in the other Macrura. Immediately
beneath the aforedescribed processes, is seen an extremely
small dentiform projection — the pterygostomial spine.
The rostrum exhibits a structural appearance diverging
considerably from that in the other known Crangonidæ.
In size it is by no means inconsiderable, at the root broad
and depressed, but from thence suddenly much compressed
laterally and securiform, constituting below a vertical plate,
closely beset along the margins with bristles. The extremity
of the rostrum is produced into a long and acute, lanceolate,
and obliquely upturned point, which projects considerably
beyond the basal segment of the 1st pair of antennæ. and
gives to the animal — lateral aspect (fig. 2) — a highly
characteristic appearance.
3
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