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99
indre Flade har to stærke Sidefordybninger, der adskilles
vecl et næsten fladt Midtparti, Fig. 12.
Ed. Perrier har i sin summariske Beskrivelse over
nye Asterider opfort to nye Arter af Slægten Koretkraster,
nemlig: Kor. palmatus og radians. Hos begge disse Arter
har han iagttaget Tentakelporer imellem Ryghudens
Kalkplader, der skulle være firkantede med indskaarne Rande,
hvorved Aabningerne for Tentakelrørene fremkomme. Dette
er ganske forskjelligt fra, hvad der finder Sted hos Koreth.
hispidus; thi her findes ingen Tentakelporer, og saadanne
kunne heller ikke forekomme, da Kalkpladerne, hvoraf
Ryghudens Skelet bestaar, ikke have noget Indsnit men ere
taglagte saaledes, at ingen Aabning findes imellem dem,
Fig. 3. 14.
Af den ovenfor leverede Beskrivelse fremgaar det, at
Korethraster vanskeligen kan henføres til nogen af de for
Asteriderne grundede Familier. Nærmest maatte den vel
henføres til Familien Asterinidce; men den adskiller sig fra
denne ved fuldstændig Mangel paa Interbrachialrum, ved
det særegne Hudskelet, som danner et sammenhængende
Kalkpantser, bærende ganske eiendommelige Paxiller. Fra
Familien Pterasteridæ, hvortil Ed. Perrier er tilbøielig til
at henføre den, adskiller den sig end mere. Den har jo
intet Hulrum paa Rygfladen, den har ingen Kalkstøtter,
der bære Ryghuden som hos Pteraster, og endelig er
Hudskelettet saa ganske forskjelligt fra denne, at der
formentlig ikke kan være Tale om at indlemme den i Familien
Pterasteridæ. Under disse Omstændigheder synes det
rimeligst at danne en ny Familie for den, som da kunde
kaldes Korethrasteridæ.
Slægtskarakter.
Leget hvælvet, 5-armet. Armene korte, meget smale
ved Grunden. Rygfladen dækket af artikulerende Paxiller
forsynede med lange Naale. Analaabningen subcentral.
Madreporpladen tæt ved Anus. Ryggens Hudskelet bestaar
af flade, taglagte Kalkplader, der danne et
sammenhængende Pantser. Bugens Hudskelet bestaar af paatvers
gaaende Kalkribber, der indtage Rummet imellem
Ambu-lacralfuren og Armens Rand. 2 Rækker Fødder med
Sugeskive uden Spikier. Ingen Pedicellarier.’
Artskarakter.
Legemet tykt. Forholdet imellem den lille og store
Radius som 1 : 4. Paxillerne paa Rygfladen bestaa af 6—
10 lange Naale, der ved deres brede Grunddel ere
forenede ved stærkt Bindevæv og danne en konkav Ledflade.
Ambulacralfuren forsynet med to Rækker flade, hule Pigge.
Paa Midten af Rummet imellem Ambulacralfuren og
Armens Rand en Række lange, ligeledes fladtrykte, hule
side of this ridge, there is a slight cavity (fig. 11). The
inner surface has two deep lateral cavities, separated
from each other by a nearly flat mesial belt (fig. 12).
Ed. Perrier in his summary description of new
Ast-eridæ, has ranked, two new species of the genus
Korethraster, namely, Korethraster palmatus and radians. In both
of these species, he has observed tentacular pores between
the calcareous plates of the abactinal integument, and which
are stated to be square, with concave margins, producing
the openings for the tentacular pores. That is perfectly
different from what is found in the case of Korethraster
hispidus, because, in it, no tentacular pores are found, and
neither could they be found, because, the calcareous plates
of which the dorsal dermal skeleton consists, have no
incision, but are imbricate, in such a manner that no
opening is left between them (figs. 3. 4).
From the above description, it is evident, that
Korethraster can not easily be assigned to any of the established
families of Asteridce. The family of Asterinidce, is the
one to which it approaches nearest, but it differs from it,
in the complete absence of interbrachial spaces, and also,
in the characteristic dermal skeleton forming a continuous
calcareous armour plating, and carrying quite peculiar
paxillæ. It differs from the family of Pterasteridæ to which
Ed. Perrier is disposed to assign it still more. It has,
for instance, no cavity on the dorsal surface. There are
no calcareous supports expanding the dorsal integument’
as in Pteraster, and finally, the dermal skeleton is so
completely different from that, that there can, presumably, be
no question of including it in the family of the
Pterasteridæ. In these circumstances, it appears most reasonable
to form a new family for it, which might be designated
Korethrasteridæ.
Generic character.
The body arched; 5-rayed. The rays short, and very
narrow at the origin. The abactinal surface covered by
articulating paxillæ furnished with long needles. The anal
aperture subcentral. The madreporite close to the anus.
The abactinal dermal skeleton consists, of flat, imbricate
calcareous plates, forming a continuous armour plating.
The actinal dermal skeleton consists, of transverse
calcareous ribs, which occupy the space between the ambulacral
furrow, and the margin of the ray. There are two series
of suckers, free from spiculæ, and with sucker disks. No
pedicellariæ.
Specific Character.
The body thick. The proportion between the disk radius
and the brachial radius is, as 1:4. The paxillæ of the
abactinal surface consist, of 6—10 long needles, which are
united at their broad basal part, by strong connective
tissue, and form a concave articulatory surface. The
ambulacral furrow is furnished with two series of flat hollow
spines. In the middle of the space between the
ambulacral furrow and the margin of the rays, there is a series
13*
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