yina, Perrier; Asteropsis, Miller & Troschel; Dermasterzas, 
Perrier; Porania, Gray; Ganeria, Gray. 
Vi skulle nu i den følgende Beskrivelse se, i hvilke 
Hovedpunkter Tylaster adskiller sig fra de her nævnte 
Slægter. 
Legemet er femstraalet, omtrent 26”” høit, med hvæl- 
vet Ryg, imedens Bugfladen er meget mindre konvex, Tab. 
XI, Fig. 1, 2. Tab. XV, Fig. 4, 5. Den store Radius er 
40”, den lille 25”, 
Armenes Længde er 18””, deres Bredde ved Grun- 
den 15”". Paa Ryggen ere de meget konvexe, paa Bug- 
siden næsten flade. Interbrachialrummene ere meget brede, 
Wo, XM, Ie, il, 8, 
\ Hele Sostjernens Rygflade har et tilsyneladende glat, 
gelatinost 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 storst Mengde 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 af- 
lange Madreporplade, Tab. XI, Fig. 1, b. Bugfladen er, 
som tidligere antydet, lidt hvælvet. 
Interbrachialrummene ere meget brede udad og be- 
satte med 3 distinkte, bueformede Rækker temmelig lange 
Pigge; imellem disse Rækker sees enkelte, noget kortere 
Pigge. Indenfor den inderste Række, altsaa nærmere Mun- 
den, 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 in- 
derste, der ligesom lukke Furen, ere de længste, Tab. XI, 
Ie, @) @ 4 ld 
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. 
long madreporite is observed @AL Ql, ii, I, Ob 
Palmipes, Linck; Disasterima, Perrier; Asteropsis, Miiller 
and Troschel; Dermasterias, Perrier; Porania, Gray; Gan- 
era, 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 
PDD on o% 
The length of the rays is 18””, and their breadth at 
the origin, is 15””, They are very convex on the abactinal 
surface, but nearly flat on the actinal surface, and the in- 
terbrachial 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 remoyed, 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, ev- 
erywhere, 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 
ternal examination (Pl. XI, fig. 
marginal plates by an ex- 
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 5”” below the anus, the somewhat ob- 
As al- 
ready 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 
@AL XUE ie, Å, a), 
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, b). 
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 
9 
