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74
Den ydre Hud, der er halv gjennemsigtig og paa
Overfladeu forsynet med en Mængde haarde, spidse
Papiller, som Følge af de i den insererede Kalknaale, Fig. 1,
forlænger sig udover Interbråchialrummene lige til
Armenes Spids, hvor den gaar over i Bugfladens
Hudbedækning. Denne danner imellem Armene en næsten vandklar
Hud, der holdes udspændt af lange Kalknaale og udgjør
Bunden i det føromtalte Hulrum, Fig. 6, a, dog saaledes,
at inderst ved hver Armrand findes en Række
halvmaane-formige Aabninger, Fig. 2, hvorved Hulrummet
korresponderer med det ydre Medium. Huden paa Ryg- og
Bugfladen er i den fri Rand af Interbrachialrummet
sammen-voxet i et Par Millimeters Bredde, hvorved den her faar
nogen Lighed med en Svømmefinne.
Den indre Hud, der er temmelig tynd, dækker den
øverste Del af Maven med dens Blindtarme samt
Æggestokkene og forlænger sig udover Armenes Ryg, som den
ganske beklæder; nu bliver den yderst tynd, idet den gaar
over paa Bughuden, hvor den giver denne med dens lange
Naale et fuldstændigt Overtræk. En Fortsættelse af denne
Hud danner en meget tynd og gjennemsigtig Membran,
der beklæder samtlige Paxiller.
I Centruin af Hulrummets Bund tindes
Analaabnin-gen, Fig. 7, a, der er lidt aflang og noget fremspringende,
forsynet med en Sphincter og omgivet af 2 store, noget
aflange Kalkplader, Fig. 7, b, og 8—16 mindre, lignende,
Fig. 7, c, hvilke alle ligge paa den underste Flade af den
indre Ryghud. De to store Plader, der ligge en paa hver
Side af Analaabningen, nærme sig med deres ydre,
afrundede Rand til de to første Ambulaeralplader paa de
til-grændsende Arme; de øvrige, mindre ligge i to adspredte
Grupper. Dette Analfelt begrændses udad af en Kalkring,
der dannes af 5 Interbrachialstykker, Fig. 7, d, d.
Enhver Interbrachialplade bestaar af en Midtdel, der
er smal, lang og flad, strækker sig fra den øverste Del af
Ryggen og bøier sig ned imod Bugfladen, Fig. 8, a. 9, a.
Den er tidt udhulet efter Længden, og fra saavel dens
øverste som nederste Ende udgaa bueformige Processer,
Fig. 8, b, c. 9, b, c. De øverste Processer støde til de
tilsvarende fra de to tilgrændsende, interbrachiale
Kalkplader, hvorved Ringen sluttes, Fig. 7; de underste derimod
forene sig med lignende Processer fra en anden
underliggende Interbrachialplade, Fig. 7, e, der senere skal
beskrives.
Paa de øverste Processer, Fig. 8, b, støtte sig de 5
store Paxiller, der omgive Analfeltet, Fig. 7,/. Disse
Anal-paxiller have en Basaldel, der dannes af 4 lange, lidt
bue-dannede Rødder, Fig. 8, d, hvoraf de inderste, Fig. 8, e,
The outer integument is semi-translucent, and is
furnished on the superior surface, with a multitutude of hard
acuminate papillæ; formed in consequence of the calcareous
needles (PI. XIII, fig. 1) which are inserted in it. It
extends beyond the interbrachial spaces, and close up to the
tip of the rays, at which point, it passes into the
integumental covering of the actinal surface. Between the rays,
it becomes a nearly pellucid integument held expanded by
long calcareous needles, forming thus, the base or bottom
of the chamber already referred to (Pl. XIII, fig. 6, a)
in such manner, however, that upon each rays margin,
there is observed at the inmost part, a series of crescent
shaped openings (Pl. XIII, fig. 2), by which the chamber
is enabled to communicate with the exterior medium. In
the free margin of the interbrachial space, the integument
of the abactinal and actinal surfaces, is concreted, to the
extent of about 2mm in breadth, and this imparts, some
similarity in appearance, to the fin of a fish.
The inner integument is rather thin, and covers the
superior portion of the stomach and attached cæca, and
also the ovaries; extending then over the abactinal surface
of the rays, and completely covering them. In passing over
into the actinal surface, it becomes extremely thin, and
completely encases it, as well as, the long pertaining
calcareous needles. A continuation of this integument forms a
very thin and transparent membrane, which clothes all
the paxillæ.
The anal opening appears in the middle of the base
of the chamber (Pl. XIII, fig. 7, a). It is slightly oblong and
somewhat prominent, and is furnished with a sphincter; it
is also surrounded by two large, somewhat oblong,
calcar-erous plates (Pl. XIII, fig. 7, b) and also, with 8—16
similar but smaller plates (Pl. XIII, fig. 7, c) all of which
rest on the inferior surface of the inner dorsal integument.
The two large plates, which are placed one on eaçh side
of the anal aperture, approach with their exterior rounded
margin, to the two anterior ambulacral plates of the
adjoining rays, whilst, the other smaller plates are situated in
two separate groups. This anal aperture is bordered,
exteriorly, by a calcareous ring, formed of five interbrachial
ossicles (Pl. XIII, fig. 7, d, d). Each interbrachial plate
consists, of a narrow, long and flat mesial portion,
extending from the superior dorsal part of the animal, and
curving downwards towards the ventral surface (Pl. XIII, fig,
8, a. 9, a). It is slightly hollowed, lengthwise, and
arcuate processes proceed from both its superior and inferior
extremities (Pl. XIII, fig. 8, b, c. 9, b, c). The superior
processes butt with the corresponding processes of the two
adjoining calcareous interbrachial plates, and thus complete
the ring (Pl. XIII, fig. 7). On the other hand, the
inferior processes unite to similar processes from another
interbrachial plate placed beneath (Pl. XIII, fig. 7, e),
and which will subsequently he described.
The five large paxillæ which surround the anal area
(Pl. XIII, fig. 7, f) butt with the superior processes (PI.
XIII, fig. 8, b). These anal paxillæ have a. basal part,
formed of four, long, somewhat arcuate roots (Pl. XIII,
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