Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
Asterias spitsbergensis. n. sp.
Tab. I.
Denne Søstjerne har ved første Øiekast megen Lighed
med Stichaster roseus; men ved nærmere Undersøgelse viser
den sig at være helt forskjellig.
Asterias spitsbergensis • har 5 Arme, og Forholdet
imellem den lille og store Radius er som l:41/3; Ryggen er
hvælvet, Bugen flad, Fig. 1. 3.
Armene ere temmelig tykke, lidt indknebne ved
Grunden, noget afstumpede i Spidsen, stærkt hvælvede paa Ryggen
og Siderne, hvor de ere besatte med Pigge, der paa Siderne
danne regelmæssige Længderækker, paa Ryggen
uregelmæssige Tverrækker, Fig. 2. Imellem Piggene saavel paa Skiven
som Armene er Huden nøgen og indtages af
Tentakelporer, Fig. 2.
Skiven er hvælvet, besat med større og mindre Pigge,
Fig. 2, der paa Midten gruppere sig ringformig omkring
den centrale Analaabning. Madreporpladen er noget aflang,
meget liden og findes strax ovenfor Armvinkelen, nedsænket
i Huden.
Ambulacralfuren er begrændset af 3 Rader stærke
Pigge, Fig. 3, a, af hvilke den ene vender ind imod Furen,
og her er enhver Pig ved sin Grunddels indre Side omgivet
af Pedicellarier, den anden vender udad, og den tredie,
midterste Rad har færre Pigge, fordi Adambulacralpladerne
have afvexlende 2 og 3 Pigge.
Udenfor den ydre Rad af Furepapiller sees en Række
Pigge, der ere næsten ligesaa store som Furepiggene. De
staa som oftest to og to sammen efter Længden, og enhver
af dem er ved deres Grunddels ydre Side omgivet af
Pedicellarier, Fig. 3, b. Endelig sees udenfor denne Række,
nærmere Rygsiden, en dobbelt Række smaa Pigge, der ere
omkrandsede af Pedicellarier, Fig. 3, c.
Paa Skiven findes ingen Pedicellarier, derimod ere
Armene overalt besatte med forskjelligt formede
Pedicellarier.
Pedicellarierne langs Ambulacralfuren sidde paa en
kort Stilk i smaa Grupper paa den indre Flade af Piggens
Grunddel. De ere lige (Pédicellaires droits), have en Basis,
hvis underste Del er rund, hvis øverste Del paa Midten
er forsynet med en Fremstaaenhed og paa Siderne afgiver
Asterias spitsbergensis, n. sp.
Fl I.
At first sight, this starfish appears to have much
resemblance to Stichaster roseus; on closer examination,
however, it is seen to be very different.
Asterias spitsbergensis has 5 rays, and the proportion
between the disk-radius and the brachial-radius is, as 1:41/3.
The dorsal region is rotund whilst the actinal surface is
flat, (figs. 1, 3).
The rays are rather thick, slightly constricted at their
origin, and the points are somewhat rounded. On the dorsal
and lateral surfaces, they are sharply rounded, and those
surfaces are occupied by spines, which, on the lateral
surfaces, are distributed in regular longitudinal series, whilst,
on the dorsal surface, the rows are found transverse and
placed irregularly. Between the spines of both the disk
and the rays, the integument is bare, and the seat of
tentacular pores, (fig. 2).
The disk is convex, and occupied by longer or shorter
spines, (fig. 2), which, in its mesial part, are grouped
annul-larly around the median anal opening. The madreporite is
very small, somewhat oblong, and embedded in the
integument immediately above the interbrachial angle.
The ambulacral furrow is bordered by 3 series of strong
spines, (fig. 3 a), of which, one series radiates inwards towards
the furrow, and in this situation, each spine is surrounded
on the inner side of its base with pedicellariæ. Another series
of spines radiates outwards, and the third, or mesial series,
has a smaller number of spines, owing to the adambulacral
plates having 2 and 3 spines, alternately.
Beyond the external series of furrow-papillæ, there is
visible a series of spines, which are nearly as long as the
furrow-spines. These are most frequently disposed
longitudinally, in double pairs, and each spine is environed with
pedicellariæ on the external side of its base (fig. 3, &).
Finally, outside of this series of spines, nearer the abactinal
surface, a double series of spinelets is seen, surrounded by
pedicellariæ (fig. 3, c).
No pedicellariæ are found upon the disk, but, on the
other hand, the rays are everywhere occupied with
pedicellariæ of different forms.
The pedicellariæ found along the ambulacral furrow,
occur in small groups, seated on short peduncles, situated
on the inner surface of the base of the spine. They are
recti-form, (Pédicellaires droits) with the lower part of the base
circular, whilst in the middle of their upper part, a protub-
<< prev. page << föreg. sida << >> nästa sida >> next page >>
