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rina, Perrier; Asteropsis, Müller & Troschel; Dermasterias,
Perrier; Porania, Gray; Oaneria, Gray.
Vi skulle nu i den følgende Beskrivelse se, i hvilke
Hovedpunkter TyJaster adskiller sig fra de her nævnte
Slægter.
Legemet er femstraalet, omtrent 26""" høit, med
hvælvet Ryg, imedens Bugfladen er meget mindre konvex, Tab.
XI, Fig. 1, 2. Tab. XV, Fig. 4, 5. Den store Radius er
40""", den lille 25mm.
Armenes Længde er 18""", deres Bredde ved
Grunden 15""". Paa Ryggen ere de meget konvexe, paa
Bugsiden næsten flade. Interbrachialrummene ere meget brede,
Tab. XI, Fig. 1, 2.
Hele Søstjernens Rygflade har et tilsyneladende glat,
gelatinøst Udseende, der fremkommer ved, at Cuticula med
et temmelig tykt Slimlag overtrækker de smaa,
naalefor-mige Pigge, hvormed Huden er besat.
Disse smaa Kalkpigge komme først ret tilsyne, naar
enten Overhuden med det vedhængende Slim borttages eller
ved Indtørring. De ere næsten lige, kanske lidt bredere
ved Grunden og indleirede i Huden; under Mikroskopet
vise de sig at være overalt forsynede med smaa,
tornefor-mige Fremstaaenheder, Tab. XI, Fig. 3. Imellem disse
Pigge sees Tentakelporer, hvilke findes i størst Mængde paa
Skiven, imedens de ere meget sparsomme paa Armene.
Hvor den hvælvede Rygflade gaar over i Bugfladen,
fremkommer en Rand, der ikke er meget fremspringende,
besat med temmelig store Pigge, uden at det er muligt ved
den ydre Undersøgelse at iagttage Randplader, Tab. XI,
Fig. 2. Fig. 4, a.
Analaabningen sidder i Centrum og er omgiven af
Rygfladens Pigge, der her sidde noget tættere, Tab. XI,
Fig. 1, a. Omtrent 5""" nedenfor Anus findes den lidt
aflange Madreporplade, Tab. XI, Fig. 1, b. Bugfladen er,
som tidligere antydet, lidt hvælvet.
Interbrachialrummene ere meget brede udad og
besatte med 3 distinkte, bueformede Rækker temmelig lange
Pigge; imellem disse Rækker sees enkelte, noget kortere
Pigge. Indenfor den inderste Række, altsaa nærmere
Munden, findes en Samling af lignende Pigge, der dog ikke
indtage nogen bestemt Ordning, Tab. XI, Fig. 2, d.
Ambulacralfuren er paa Midten temmelig bred og
forsynet paa hver Rand med 3 Rader Pigge, hvoraf de
inderste, der ligesom lukke Furen, ere de længste, Tab. XI,
Fig. 2, c. 4, b.
Samtlige Pigge paa Bugfladen have et tykt, hudagtigt
Overtræk, og det er dettes Tykkelse, der gjør, at man
Den norske Nordhavsexpedition. Danielssen og Koren: Asteroidea.
Palmipes, Linck; Disasterina, Perrier; Asteropsis, Müller
and Troschel; Dermasterias, Perrier; Porania, Gray;
Oaneria, Gray.
We shall now describe in the following paper, the
chief features in which Tylaster differs from the genera
named.
The body is 5-rayed, and is about 26""" thick, and, it
has an arched abactinal surface, whilst it’s actinal surface,
is much less convex (Pl. XI, figs. 1. 2, Pl. XV, figs.
4. 5). The brachial radius is 40""", and the disk-radius
25mm long.
The length of the rays is 18*""», and their breadth at
the origin, is 15mm. They are very convex on the abactinal
surface, but nearly flat on the actinal surface, and the
interbrachial spaces are very broad (Pl. XI, figs. 1. 2).
The entire abactinal surface of this starfish, has, an
apparently smooth, gelatinous appearance; produced by the
cuticle having a rather thick mucous coating; which encases
the small needle-formed spines, with which the integument
is beset.
These small calcareous spines, first become, distinctly
visible, when the outer integument with its accompanying
mucous coating is removed, or it becomes dried. They are
nearly uniform in thickness; if anything, a little broader
at the base; and they appear entrenched in the integument.
Examined with a microscope, they are seen to be,
everywhere, furnished with small aculeated prominences (PI.
XI, fig. 3). Between these spines, tentacular pores are
visible, and they are most numerous upon the disk, whilst
the rays, are very sparingly furnished.
At the point where the arcuate dorsal surface passes
into the ventral surface, a margin appears, but is not at all
prominent. It is beset with pretty large spines, although,
it is not possible to detect any marginal plates by an
external examination (Pl. XI, fig. 2. fig 4, a).
The anal aperture is situated in the middle, and is
surrounded by the spines of the abactinal surface, which
are, in this situation, placed somewhat closer (Pl. XI,
fig. 1, a). About 5mm below the anus, the somewhat
oblong madreporite is observed (Pl. XI, fig. 1, b). As
already indicated the actinal surface is slightly arcuate.
The interbrachial spaces are very broad exteriorly,
and are beset with 3 distinct arcuate series of pretty long
spines, and between these series, a few somewhat shorter
spines are seen.
Within the inmost series of spines, consequently,
nearer to the mouth; a collection of similar spines is found,
which do not however assume any regular arrangement
(Pl. XI, fig. 2, d).
The ambulacral furrow is rather broad at the mesial
part, and is furnished on each margin, with 3 rows of
spines; of which the inmost, which as it were, closes the
furrow, are the longest (Pl. XI, fig. 2, c. 4, 6).
All the spines on the actinal surface have a thick
membranous covering, and it is owing to the thickness of
this covering, that, neither in the living animal, nor in
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