finde vi, omend ikke i den Størrelse saa dog tilnærmelses- 
vis, ogsaa hos meget unge Hxemplarer af flere Arter, 
henhørende til Familien Asteropectnidæ. Ligesaa findes hos 
flere Arter af denne Familie, især 1 den yngre Alder, en 
ganske liden, konisk Fremstaaenhed paa Skivens Centrum; 
men ved at sammenstille saadanne yngre Dyr af omtrent 
samme Størrelse som Jlyaster have vi fundet, at dennes 
Fiendommeligheder ere af en saadan Beskaffenhed, at de 
neppe i nogen væsentlig Grad skulle kunne forandres ved 
Alderen, og derfor have vi fundet det nødvendigt midler- 
tidigt at danne en ny Slægt for den. 
I levende Live bærer Ilyaster det centrale Rygappen- 
dix saagodtsom opret, men det bevægede sig ved smaa 
Bøininger og havde et Udseende, som om det kunde være 
en afreven Stilk, hvorved Dyret havde været fæstet. Er 
det virkelig Rest af en saadan Stilk, har denne efter Dy- 
rets Frigjørelse undergaaet nogen Forandring; thi ved at 
undersøge den fri Ende af Appendixet, viste denne sig at 
være lidt afrundet og næsten overalt besat med de før be- 
skrevne Pigge. 
Ved den første, overfladiske Undersøgelse opstod der 
Tanke om, at Zlyaster muligens kundefvære et ungt Fx- 
emplar af Bathybiaster pallidus, med hvilken den i flere 
Punkter har noget tilfælles, men snart maatte denne Tanke 
opgives ved at sammenligne unge Exemplarer af Bathybi- 
aster med Ilyaster. Denne har ingen Pedicellarier, og der 
hvor Bathybiaster langs Bugfuren har de store, eiendom- 
melige Pedicellarier, har Jlyaster en meget stor Pig. Ily- 
aster har 4 stærke Tænder, imedens unge Exemplarer af 
Bathybiaster mangle Tænder, og de udvoxne Dyr kun have 
to. Og endelig det høist mærkelige, centrale Rygappendix, 
der ganske savnes hos Bathybiaster. 
Vi omtalte tidligere, at der hos flere Arter henhø- 
rende til Familien Asteropectmidoæ fandtes saavel hos yngre 
som ældre Dyr en ganske liden, konisk Fremstaaenhed paa 
Midten af Skivens Rygside; men undersøger man denne 
Fremstaaenhed, vil man altid finde, at den har samme 
Paxillarbeklædning som hele den øvrige Del af Skivens 
Ryg; noget anderledes er det med Rygappendixet hos Ily- 
aster. Beklædningen er her forskjellig fra Skivens, saa at, 
om man end kunde være tilbøielig til i morphologisk Hen- 
seende at betragte Rygappendixet som en høiere Udvikling 
af den ovennævnte lille, koniske Knop, har det dog 
under alle Omstændigheder undergaaet Forandringer, der 
giver Ilyaster et fra alle andre hidtil kjendte Søstjerner 
forskjelligt Udseende. Men vi ere tilbøielige til at antage, 
at den oftere omtalte lille, central-dorsale Fremstaaenhed 
hos Asteropectiniderne er en Levning af en fordums Stilk, 
hvorved Dyret har været fæstet, — en Antagelse, der i 
hoi Grad vinder i Styrke, efter at man er bleven bekjendt 
med Rygappendixet hos Jlyaster, hvilket unægtelig peger 
hen paa Embryonalstadiet hos Crinoiderne. Det forekom- 
mer os saaledes meget sandsynligt, at vor Zlyaster har havt 
et saadant Larvestadium, og at den selv frigjort altid vil 
komme til at bære kjendelige Spor efter dette sit tidligste 
Ungdomsliv. Men forholder dette sig saa, da have vi for- 
102 
the tip of the rays are also met with, if not of the same 
size, still approximately so, in very young specimens of 
several species pertaining to the family of Asteropectimidæ. 
There is also found in several species of that family, es- 
pecially in the younger specimens, a quite small, conical 
protuberance, in the centre of the disk, but, on a compari- 
son of such young animals, of about the same dimensions 
as Ilyaster, we have found, that its peculiarities are of 
such a character, that they can, scarcely, in any material 
degree, be changed by age, and we have, therefore, found 
it necessary, meantime, to form a new genus for it. 
During life, Ilyaster carries its central dorsal 
appendix, almost erect, but it moves in small wavings, and 
has an appearance as if it were a detached peduncle, by 
which the animal had been secured. If it really is the 
remnant of such a peduncle, it must, subsequent to the 
detachment of the animal, have undergone some change, be- 
cause, on examining the free extremity of the appendix, it 
is seen to be slightly rounded, and nearly everywhere, be- 
set with the spines previously described. 
On the first superficial examination, the thought oc- 
curred, that Zlyuster might, perhaps, be a young specimen 
of Bathybiaster pallidus, which in several features it re- 
sembles, but that thought was speedily abandonned, when 
we had compared young specimens of Bathybiaster, with 
Ilyaster. The latter has no pedicellariæ, and im the situa- 
tion along the ventral furrow, where Bathybiaster has the 
long characteristic pedicellariæ, Ilyaster has a very large 
spine. Jlyaster has four strong teeth, whilst young speci- 
mens of Bathybiaster have no teeth, and the full grown 
animal has only two teeth. Finally, we have the highly 
remarkable dorsal appendix, which is completely awanting 
in Bathybiaster. 
We stated previously, that in several species pertain- 
ing to the family of Asteropectinidæ there was found, both 
in the young, as well as in the old animals, a quite small, 
conical protuberance in the middle of the abactinal disk, 
but, when the protuberance is examined, it is always found 
to have the same paxillar clothing, as all the rest of 
the abactinal disk, but this is not the case with the ap- 
pendix of Zlyaster. The covering, here, is different from 
that of the disk, so that, even, if we were disposed to 
eonsider the appendix from a morphological point of view, 
as a higher development of the above named small conical 
knob; it must still, in every case, have undergone changes 
which gives Zlyaster a different appearance from all other 
starfishes hitherto known. But we are disposed to assume, 
that the frequently mentioned, small, central dorsal protub- 
erance in Åsteropectmidæ, is a remnant of a former pe- 
dunele by which the animal has been secured, an assump- 
tion which is greatly strengthened after becoming acquainted 
with the dorsal appendix in Jlyaster, which, undoubledly, 
points towards the embryonal stage im Crinoidea. It ap- 
pears to us, therefore, most probable, that our Llyaster has 
passed such a larva-stage, and that, even when detached, 
it will always afterwards bear recognisable trace of its ear- 
liest embryo period. If this is the case, we are, presum- 
