Denne Søstjerne er regelmæssig femkantet og temmelig 
flad. Rygsiden hvælver sig noget henimod Centrum, hvor 
der er en traktformig Fremstaaenhed, paa hvis Spids fin- 
des en Aabning, Tab. XIII, Fig. 1. Tab. XV, Fig. 7. 
Denne, der kan stærkt udvides og bliver da femkantet, fø- 
rer ind til et stort Hulrum, som indtager Størstedelen af 
Ryggen. 
Bugsiden er flad, og i dens Centrum findes den runde 
Mundaabning, hvorfra udgaa de 5 Bugfurer, forsynede med 
2 Rækker konisk tilspidsede Fodder uden Spikler, Tab. 
XIII, Fig. 1. Tab. XV, Fig. 8, og 1 Række Furepapil- 
ler, der ere saaledes stillede, at to og to staa sammen og 
vende ind til Ambulacralfuren, Tab. XIII, Fig. 2, a. 3, a. 
Udad, omtrent midt imellem disse Ambulaeralpapiller, 
sees paa hver Adambulacralplade en tyk, konisk tilspidset Pig, 
Tab. XTIT, Fig. 2,6. 3,0, der er ganske eiendommelig, og som 
indtager en halvmaaneformig Aabning, Fig. 2, c. 3,¢, som 
findes imellem de lange Kalknaale, Fig. 2, d. 3, d, der 
udspænder Huden over Interbrachialrummet, og 
for skulle omtales. 
som neden- 
Denne særegne Pig, Fig. 4, ved 
sin runde Basaldel, paa hvilken findes en konkav Led- 
flade, Fig. 4, a. 5, a, omgiven af et Kalkgitter, Fig. 4, b. 
5, b, der udgaar vifteformigt fra Grunddelen, og hvis øvre, 
frie Rand ender i 5 lange Spidser, imellem hvilke der er 
Indskjæringer, Fig. 4, c. 
er 
Hele Piggen er indesluttet i en 
blæreformig Membran, Fig. 5, c, der udspændes af det 
ovenfor beskrevne Kalkgitter. Paa den undre Flade af 
denne Membran sees to listeformige Rande, Fig. 5, d, 
imellem hvilke er et bredt, afplaneret Belte, Fig. 5,6, der 
gjør en Boining nedover Basaldelen og bliver smalere, idet 
det forlænger sig opad til noget over Midten. Denne Pig 
med sit særegne, membranøse Hylster lukker ganske den 
halvmaaneformige Aabning imellem de lange Kalknaale og 
virker ved sine stærke Muskler som en Klappe: 
De lange Kalknaale, Fig. 17, der udspænde Bughu- 
den, have paa sin noget brede, til Siden udvidede Basal- 
del, Fig. 17, a, en aflang, hul Ledflade, Fig. 17,0. 
Selye Naalen er sammensat af yderst fine, lange Kalkstave, 
der ved Tverprocesser ere forenede med hverandre, Fig. 17,c. 
Ligesom hos Slegten Pteraster har denne Sostjerne 
en dobbelt Hud, en ydre og en indre, hvilket Forhold især 
er fremtrædende paa Rygfladen, hvor den ydre Hud støt- 
tes op og bæres af en Mengde Paxiller, hvorved Hvælvet 
for det nævnte Hulrum dannes. 
Den norske Nordhaysexpedition, Danielssen og Koren: Asteroidea. 
In shape, this starfish is a regular formed pentagon, 
and rather flat. The abactinal surface arches a little to- 
wards the centre; and at this point, there is a funnel- 
shaped protuberance, in the middle of which, there is an 
opening (Pl. XIII, fig. 1, Pl. XV, fig. 7). This promin- 
ence is capable of great extension, and when expanded, 
assumes a pentagonal form. It forms a passage into a 
large cavernous chamber, which includes the principal part 
of the abactinal disk. 
The actinal surface is flat; and im its middle is found, 
the circular oral opening from which the five ventral fur- 
rows proceed. Each of these is furnished with two series 
of coniform, acuminate suckers free from spiculæ (Pl. XIII, 
fig. 1, Pl. XV, fig. 8), and also, one series of furrow-pap- 
ille; arranged in such manner, that two and two are placed 
together, and radiate towards the ventral furrow (PI. XIII, 
fies 2) a. 3, a): 
Exteriorly, and near the middle, there is visible be- 
tween these ambulaeral papillæ; a thick, coniform, acuminate 
spine, carried on each adambulacral plate (Pl. XIII, fig. 
2, b. 3, b). This spine is quite peculiar, and it includes 
a crescent formed aperture (Pl. XIII, fig. 2,¢. 3,0), which 
appears between the long calcareous needles (Pl. XIII, 
fig. 2, d. 3, d); expanding the integument over the inter- 
brachial space, and subsequently be referred to. 
This peculiar spme has a concave articulatory surface 
(Pl. XIII, fig. 4, a. 5. a) situated upon its round basal 
part, and this part is also surrounded by a_ calcareous 
erating (Pl. XIII, fig. b. 4, b), extending from the base 
in a fan shape; the superior free margin terminates in 
five long points, with intermedial incisions (Pl. XIII, fig. 
4, c). The whole of the spine is enclosed in a vesicular 
membrane (Pl. XIII, fig. 5, c) which is held expanded by 
the above described calcareous grating. On the inferior 
surface of this membrane, two fillet-formed margins are 
seen (Pl. XIII, fig. 5, d), and between these, there is a 
broad smooth flat border (Pl. XIII, fig. 5, e), curving 
downwards over the basal part, and becoming narrower, 
as it becomes prolonged upwards to a little beyond the 
middle part of the vessicle. This spine and its peculiar 
will 
membranous casing, completely closes the crescent formed 
opening between the long calcareous needles, and by means 
of it’s powerful muscles, serves as a flap to the aperture. 
The long caleareous needles (Pl. XIII, fig. 17) serv- 
ing to expand the actinal integument, have an oblong hol- 
low articulatory surface (Pl. XIII, fig. 17,0) situated upon 
their somewhat broad, laterally expanded, basal part (PI. 
XIII, fig. 17, a). The needle itself, is composed of ex- 
tremely fine long calcareous rods, which are united by 
transverse processes to each other (Pl. XIII, fig. 17, c). 
Just as there is a double integument found in the 
genus Pteraster, so is there, also, an outer and inner integ- 
ument in this starfish; and this is specially prominent on 
the abactinal surface; in which situation, the outer integu- 
ment is supported and borne up by a multitude of pax- 
illæ; forming thus, the arched roof of the cavity previously 
spoken of. 
10 
