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97
tidligere beskrevne Paxillerækker og ere egentlig
sammensmeltede, saa at hele Ryghudens Skelet dannt*r et
fuldstændigt Kalkpantser uden Tentakelporer, Fig. 3.
Sammensmeltningen er næsten overalt saa komplet, at det har
sine Vanskeligheder at skille Pladerne fra hverandre.
Bugen er flad, og her fremtræder Armenes særegne
Form meget tydeligt. Intet Interbrachialrum, Fig. 2.
Ambulacralfuren er ikke meget bred, forsynet med 2
Rækker cylindriske Fodder, som ere uden Spikier men
have en vid Sugeskive. Furens Rand har to Rader Pigge,
hvoraf den ene er lidt indenfor og under den anden, Fig.
8, a. Piggene i den inderste Rad ere de længste, forresten
er Formen den samme. De have et noget fladtrykt Udseende
men danne egentlig en hul Halvcylinder, der er bredere i
den næsten spatelformige, frie Ende, hvis Rand er
krene-leret, Fig. 9, a, imedens den smalere Del er rund, ikke
hul, og har en Ledflade, Fig. 9, b, der artikulerer med en
tilsvarende rund Knop paa Adambulacralpladen. Disse
Pigge ere efter Lamgden forsynede med mange Rækker
fine, næsten runde Huller og have et Hudovertræk.
Udenfor Furepiggene findes omtrent paa Midten af
Rummet imellem Ambulacralfuren og Armens Rand en
Række Pigge, fuldkommen lignende de nys beskrevne,
kun ere de noget længere. Fig. 8, e. Endelig findes paa
Armens Rand en 4de Række Pigge, der ere forskjellige
fra de øvrige, og som vi ville kalde Randpigge, Fig. 8, f.
10. De ere smale ved deres Grunddel, der er rund og
forsynet med en Ledflade, Fig. 10, a, og udvider sig
blad-formigt mod den frie Ende, som har. 5 temmelig lange
Spidser, Fig. 10, b, hvoraf de to, der danne Hjørnespidserne,
ere de korteste. Den bladformige Del har noget indbøiede
Rande, hvorved fremkommer en Hulhed, der er dybest ned
imod Basaldelen og er forsynet med Længderibber,
imellem hvilke sees 4—5 Rækker rundagtige Aabninger, Fig.
10, c. Hele Piggen er omgiven af en temmelig tynd,
halv gjennemsigtig Hud. Disse Pigge findes kun paa
Armens frie Rand, det vil sige paa den Del, der er imellem
det før beskrevne Vinkelhjørne og Armens Spids; paa den
indre Armrand findes ingen.
I enhver Arinvinkel sees en stor, lidt konkav, nøgen
Kalkplade, der ganske indtager den hele Vinkel, har en
triangulær Fonn, støtter sig til Siderne ved sine lange
Udløbere til Adambulacralpladerne og indad til
Mundpladerne, Fig. 8, b.
Mundpladerne, Fig. 8, c, der ere Forlængelser af
Adambulacralpladenie, have paa deres afrundede, frie Rand
Den norske Nordhavsexpedition. Danielsscn og Koren Asteroidea.
All the calcareous plates are closely imbricate, and form
regular series (fig. 3) which completely correspond with
the previously described paxillar series. They, really, are
merged in each other, so, that the entire abactinal dermal
skeleton forms a complete calcareous armour, having no
tentacular pores (fig. 3). The intermerging, is, nearly
everywhere, so complete, that to separate the plates from each
other, is not accomplished without difficulty.
The actinal surlace is flat, and in this situation, the
peculiar form of the rays becomes very prominent. There
is ho interbrachial space (fig. 2).
The ambulacral furrow is not verv wide, and is
furnished with two series of cylindric suckers free from
spic-ulæ, but with a broad sucker-disk. The furrow’s margin
is furnished with two series of spines, of which, one is
placed a little inside, and below the other (fig. 8, a). The
spines of the inner series are the longest, but otherwise,
the form is the same. They have a somewhat flattened
appearance, but, really, form a demi-cylinder, which is
broadest at the almost spatulate free extremity, and whose
margin is crenate (fig. 9, a) whilst the narrower portion
is round, and not hollow, and is furnished with an
artic-ulatory surface (fig. 9, b) articulating with a
corresponding round knob on the adambulacral plate. These spines
are furnished, longitudinally, with numerous series of minute
nearly round perforations, and are clothed with an
integu-mental covering.
Beyond the furrow spines, and about the middle of
the space between the ambulacral furrow and the margin
of the ray, there is found, a series of exactly similar spines
to those just described, except, that they are much longer
(fig. 8, e). Finally, there is found on the margin of the
ray, a fourth series of spines, which are different from the
rest, and we shall designate them marginal spines (fig. 8,/.
10). These are narrow at the basal part, which is round,
and furnished with an articulatory surface (fig. 10, a), and
they expand in a leaf-shape towards the free extremity,
upon which, five rather long points are situated (fig. 10, b),
of which points, the two forming the angular apex points
are the shortest. The margins of the leaf-formed part are
somewhat curved inwards, producing a cavity, which is
deepest down towards the basal part, and it is furnished
with longitudinal ribs, between which, 4—5 series of
roundish apertures are seen (fig. 10, c). The entire spine is
surrounded by a rather thin semi-transparent integument.
These spines are found, only, on the free margin of the
ray, that is to say, on the portion situated between the
previously described angular apex and the tip of the ray.
None are found on the inner margin of the ray.
In each brachial angle, a large, slightly concave, bare,
calcareous plate is seen, which quite includes the whole of
the angle, and has a triangular form, and it abuts
laterally by means of its long prolongations, on the
adambulacral plates, and inwards, on the oral plates (fig. 8, b).
The oral plates (fig. 8, c) are prolongations of the
adambulacral plates, and have, upon their free rounded
is
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