for den indre, halykugleformige Fremstaaenhed, der tjener 
til Støtte for Ambulacralpladens Tverproces, udspringe to 
temmelig lange Kalkpigge, der tage deres Retning indad 
mod Bugfuren, hvis halve Bredde de indtage, Fig. 2, a. 5. 
13, d. Samtlige disse Pigge ere forsynede med konkave 
Ledflader, der svare til de smaa, runde Forhoininger paa 
Midtparti.  Foruden disse 3 artiku- 
paa en stor Del af de imdre Adam- 
en 4de Pig, der sidder omtrent midt 
imellem de 2 store Randpigge; den er temmelig kort og 
har en bred Basis. Det første Par Adambulacralplader 
smelte sammen med de tilsvarende fra hver tilgrændsende 
Arm og danne derved de 5 Mundvinkelplader. Disse ere 
tykke, stærke, aflange, med en Som efter Midten og forsy- 
nede med 6 lange (3 paa hver Side) tilspidsede, articule- 
rende Kalkpigge (Tænder), der vende ind mod Mundaab- 
ningen, Fig. 2. 
Adambulacralpladens 
lerende Pigge findes 
bulacralplader endnu 
Paa Bunden af den store Ryghule, 1 et Interbrachial- 
rum paa Grunden af en Arm, sees Madreporpladen, Fig. 
7, 7, der er ægdannet med den bredere Del indad. Den 
har en bred Basis, hvis ophøiede Rand slutter sig til det 
Sideindsnit, som findes paa den øverste Interbrachialplade, 
Fig 7, d.  Overfladen er lidt konvex, riflet paatvers 
(mæandrisk furet) og noget nedsunken 1 den indre Ryghud. 
Den ydre Ryghud, der som tidligere omtalt støttes 
af Paxillerne, har en Mængde større og mindre, aflange 
Huller (Spiracula), Fig. 14. 15. 16, a. Den bestaar af en 
glat, gjennemsigtig, strukturløs Cuticula, et cellerigt Fpithel 
og saa den egentlige Cutis, som dannes af Bindevævsbund- 
ter, der ligge i forskjellige Retninger tæt til hverandre. 
Indenfor Cutis er en Bindevævshud, som er rig paa Musk- 
ler, der krydse hverandre, og som især samle sig omkring 
de førnævnte Aabninger, Fig. 14. 15. 16, b. Denne Mu- 
skelhud, der er beklædt med et cilierende Hpithel, stræk- 
ker sig ikke alene nedover de Totrediedele af Paxillarnaa- 
lene, som den beklæder, Fig. 15, c, men ogsaa udover de 
aflange Aabninger, som derved paa den indre Side faar en 
uregelmæssig Form, Fig. 16. 15, d. Saavel omkring disse 
Aabninger som omkring de halvmaaneformige Aabningers 
Rand er Celleepithelet stærkt fortykket, Fig. 14, c, men 
nogen Ringmuskel findes ikke omkring dem. 
Hullerne (Spiracula) i Ryghuden med den ovenom- 
talte Muskelanordning og de semilunære Ventralaabninger 
med deres eiendommelige Klapper, kunne lukkes og aabnes 
efter Omstændighederne og staa aabenbart i Aandedræt- 
tets Tjeneste. Noget lignende finder ogsaa Sted hos Slæg- 
78 
and nearly at the middle, an acuminate calcareous spine 
projects in an outward direction (Pl. XIII, fig. 2, c. 5. 
11, Å) and is observed, between the two long calcareous 
needles on the actinal surface. Immediately above the 
inner spherical prominence which serves as a support for 
the transverse process of the ambulacral plates, two rather 
long calcareous needles project, and are directed inwards, 
towards the ventral furrow, covering it, for half of its 
breadth (Pl. XIII, fig. 2, a. 5. 13, d). Both of these 
spines are furnished with concave articulatory surfaces, 
corresponding with the two small round prominences of 
the adambulacral plates mesial part. Besides these three 
articulating spines, yet a fourth spine is found, on a great 
many of the inner adambulacral plates; situated about mid- 
way between the two large marginal spines. 
is rather short and has a broad base. The first pair 
of adambulacral plates interunite with the correspond- 
ing ones from each adjoming ray, and form, thus, the five 
oral angle plates. These are thick, strong and oblong, 
with a suture along the mesial lme, and they are fur- 
nished with six long (3 on each margin) acuminate articul- 
ating calcareous spines (teeth) which face inwards towards 
the oral aperture (Pl. XIII, fig. 2). 
At the base of the large dorsal chamber, the mad- 
reporite is seen, seated in an interbrachial space at the 
origin of a ray (Pl. XIII, fig. 7,2). It is ovate in shape, 
with it’s broad part turned inwards, and it has a broad 
base, whose elevated margin joins the lateral incision ob- 
served on the superior interbrachial plate (Pl. XIII, fig. 
7, d). The superior surface is slightly convex, ridged 
transversely, and intersected by meandering furrows. It 
This spine 
is somewat depressed in the inner dorsal integument. 
The outer dorsal integument is, as previously stated, 
supported by the paxille, and has a multitude of larger 
or smaller, oblong pores in it (spiracles) (Pl. XIII, fig. 14. 
15. 16, a). It consists of a smooth transparent structure- 
less cuticle, and a compact cellular epithelium, besides the 
genuine cutes formed of bundles of connective tissue dis- 
tributed close to each other, but extending in different di- 
rections. Inside the cutes, there is a membrane of mus- 
culous connective tissue, in which muscles cross each other, 
and the muscles are especially centred around the previ- 
ously mentioned apertures (Pl. XIII, figs. 14. 15. 16, 0). 
This muscular integument is clad with a fimbriate epithel- 
ium, and extends, not only, down over two third parts of 
the paxillar needles included by it (PI. XIII, fig. 15, c) 
but also, out over the oblong apertures, and these obtain in 
this manner, an irregular form upon the inner margin (PI. 
XIII, fig. 16. 15, d). Both, around these apertures, as 
well as, around the margins of the crescent formed aper- 
tures, the cellular epithelium is greatly tumified (PI. 
XIII. fig, 14, c) but no annular muscle is found about it. 
The pores (spiracles) of the dorsal integument and 
the semilunar ventral apertures, with their peculiar flaps, 
can be shut or opened by means of the above described 
muscular to circumstances, and 
clearly pertain to the respiratory system. Something sim- 
arrangement according 
