Paxiller er fladtrykt, har en bredere, afrundet Ende, der 
er forsynet med 7 smaa, runde Artikulationsflader, som 
artikulere med de 7 (4 lange og 3 korte) Kalknaale, Fig. 9, ¢, 
der vifteformigt udbrede sig i Armenes Ryghud, Fig. 1, d. 
Skelettet paa et fuldvoxent Exemplar (50"” T'vervidde) 
bestaar af 28 Par Ambulacralplader, hvortil fæster sig li- 
gesaa mange Adambulacralplader. Hver Ambulacralplade 
bestaar som sædvanligt af et Midtparti og en Sideforlæn- 
gelse (transversel Proces). Midtpartiet, Fig. 10. 11. 12, a, 
er meget bredt indad, men bliver smalere udad og danner 
en flad Trekant. Det har 3 Flader; den indvendige, som 
er den største og bredeste, forener sig med den tilsvarende 
fra den modsatte Side, hvorved det saakaldte Vertebrum 
fremkommer; den øverste Flade, Fig. 10. 11. 12,0, er 
lidt konvex til Siderne, den underste er lidt konkav. Saa- 
vel Over- som Underfladen er forsynet med hver sin Arti- 
kulationsflade, der artikulerer med den tilsvarende Flade 
Paa 
Sideforlængelsen er 
paa den over- og underliggende Ambulacralplade. 
denne Maade fremkommer NSøilen. 
smal, hvor den udgaar fra Midtpartiet, men bliver alt bre- 
dere og bredere, gaar i en skjæv Retning udad og har 
paa sin ydre, afrundede Rand et lidet, halvrundt Indsnit, 
Fig. 10. 11. 12, « Den øverste, frie Flade er konvex, 
den underste har en konkav, lidt aflang Ledflade. Det 
første Par Ambulacralplader (nærmest Munden) ere de 
største, deres Midtparti er temmelig tykt og langt og for- 
længer sig lidt til Siderne udad mod Interbrachialrummene, 
hvor de nærme sig de tilsvarende Sidearmes første Ambu- 
lacralplader, uden at de dog ganske støde sammen, 
hvorved der fremkommer en stump Vinkel, hvis Konkavi- 
tet vender mod Munden. Ambulacralpladerne aftage i 
Størrelse, alt eftersom de nærme sig Armens Spids, hvor 
de ere yderst smaa. 
Adambulacralpladerne, 28 paa hter Side, ere tem- 
melig smaa, have en aflang Figur, lidt indkneben paa Mid- 
ten og bredere i beggeiEnder, Fig. 11,d. Den øverste, af- 
rundede Ende, har paa sin øverste Flade (den, der vender 
mod Armens Rygflade) en aflang, fremstaaende Ledflade, 
Fig. 13, a, der artikulerer med en tilsvarende udhulet 
Ledtlade paa den ovenfor (indenfor) liggende Adambula- 
eralplade, Fig. 13,b. Paa den nederste Ende, der er næs- 
ten tvers afskaaren, findes den ovennævnte aflange, udhu- 
lede Ledflade. Denne nederste Ende udvider sig til Si- 
derne og danner ligesom to kugleformige Fremstaaenheder, 
Fig. 11, f. Paa den ydre af disse (den, der vender mod 
Interbrachialrummet) er lige paa Randen en liden, rund 
Ophøining, der danner Ledfladen for den store, lange 
Kalknaal, som bidrager til at udspænde den gjennemsigtige 
Hud paa Bugfladen, Fig. 2, d. 11, g. 13, c.  Lidt 
for, næsten paa Midten, udspringer en tilspidset Kalkpig, 
Fig. 2, c. 5. 11, h, der har en Retning udad og findes 
imellem de to lange Kalknaale paa Bugsiden. Strax oven- 
oven- 
77 
(PL XM ie, 9, gj 
flattened, and has a broadish rounded extremity, furnished 
with 7 small, circular, articulatory surfaces, which articulate 
with the 7 (4 long ones and 3 short ones) calcareous 
needles (Pl. XIII, fig. 9, ¢) that spread as a fan in the 
dorsal integument of the rays (Pl. XIII, fig. 1, d. 
The skeleton of a full grown specimen (50"” in di- 
ameter), consists of 28 pairs of ambulacral plates, to which, 
an equal number of adambulacral plates are fastened. Hach 
The shaft of the inner paxillæ is 
ambulacral plate consists, as usual, of a mesial part, and 
a lateral prolongation (transverse process). The mesial part 
(Pl. XIII, fig. 10. 11. 12, a) is very broad mwards, but 
It 
has three surfaces, of which, the inner one is the largest 
and broadest, and unites with the corresponding ones from 
becomes narrower outwards, and forms a flat triangle. 
the opposite margin, producing the so-called vertebrum. 
The superior surface (Pl. XTIT, fig. 10. 11. 12, b) is a 
little convex laterally, whilst, the inferior surface is slightly 
concave. Both the superior and inferior surfaces are fur- 
nished, with an articulatory surface, articulating with the 
corresponding surface of the superior and inferior ambul- 
acral plates. In this the column is produced. 
The lateral prolongation is narrow, where it springs from 
manner, 
the mesial part, but becomes broader and broader, and 
proceeds in a curved direction outwards, and it has a 
small semicircular incision (Pl. XIII, fig. 10. 11. 12, c) 
upon its exterior rounded margin. The superior free sur- 
face is convex, whilst, the inferior surface has a slightly 
oblong, concave articulatory surface on it. The first pair 
(nearest the oral aperture) of ambulacral plates are the 
largest, and their mesial part is pretty thick and long. - 
They become elongated, laterally, towards the mterbrachial 
spaces, and approach the first ambulacral plates of the 
corresponding adjoining rays, not, however, quite butting 
obtuse angle, with it's con- 
The ambulacral plates dim- 
with these, but producing an 
cavity facing the oral opening. 
inish in size, according as they approach to the tip of the 
rays, at which point they become extremely small. 
There are 28 adambulacral plates on each margin; 
these are rather small, and have an oblong shape, slightly 
constricted at the middle, and becoming broader towards 
the extremities (Pl. XIII, fig. 11,d). The superior rounded 
extremity has, upon its upper surface (the surface which 
turns towards the abactinal surface of the ray) an oblong 
protuberant articulatory surface (Pl. XIII, fig. 13, a) ar- 
ticulating with a corresponding hollow articulatory surface 
on the superior (interior) adambulacral plate (Pl. XIII, 
tes Sb): 
upon it, is seen, the above mentioned, oblong, hollow artic- 
The inferior extremity is nearly truncate, and 
ulatory surface. This inferior extremity expands laterally, 
and forms, as it were, two spherical prominences (PI. XIII, 
fig. 11, f). On the exterior one of these (the one which 
faces towards the interbrachial space), close to the margin, 
there is a small round elevation, which forms the articul- 
atory surface, for the large, long calcareous needle contrib- 
uting to expand the translucent integument of the ventral 
Suntacer (kyle Nella tion 2 Syd salle gil 3 560) Aenlittlerabove 
