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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, t,
der vifteformigt udbrede sig i Armenes Ryghud, Fig. 1, d.
Skelettet paa et fuldvoxent Exemplar (50""" Tvervidde)
bestaar af 28 Par Ambulacralplader, hvortil fæster sig
ligesaa mange Adambulacralplader. Hver Ambulacralplade
bestaar som sædvanligt af et Midtparti og en
Sideforlængelse (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, b, er
lidt konvex til Siderne, den underste er lidt konkav.
Saavel Over- som Underfladen er forsynet med hver sin
Arti-kulationsflade, der artikulerer med den tilsvarende Flade
paa den over- og underliggende Ambulacralplade. Paa
denne Maade fremkommer Søilen. Sideforlængelsen er
smal, hvor den udgaar fra Midtpartiet, men bliver alt
bredere og bredere, gaar i en’ skjæv Retning udad og har
paa sin ydre, afrundede Rand et lidet, halvrundt Indsnit,
Fig. 10. 11. 12, c. 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
forlænger sig lidt til Siderne udad mod Interbrachialrummene,
hvor de nærme sig de tilsvarende Sidearmes første
Ambulacralplader , 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 hver Side. ere
temmelig smaa, have en aflang Figur, lidt indkneben paa
Midten og bredere i begge Ender,’ Fig. 11 ,[d. Den øverste,
afrundede 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
Ledflade paa den ovenfor (indenfor) liggende
Adambula-cralplade, Fig. 13, b. Paa den nederste Ende, der er
næsten tvers afskaaren, tindes den ovennævnte aflange,
udhulede Ledflade. Denne nederste Ende udvider sig til
Siderne og danner ligesom to kugleformige Fremstaaenheder,
Fig. 11, /. 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
ovenfor, 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-
(Pl. XIII, fig. 9, q). The shaft of the inner paxillæ is
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, t) that spread as a fan in the
dorsal integument of the rays (PI. XIII, fig. 1, d.
The skeleton of a full grown specimen (50mm in
diameter), consists of 28 pairs of ambulacral plates, to which,
an equal number of adambulacral plates are fastened. Each
ambulacrqj 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 inwards, but
becomes narrower outwards, and forms a flat triangle. It
has three surfaces, of which, the inner one is the largest
and broadest, and unites with the corresponding ones from
the opposite margin, producing the so-called vertebrum.
The superior surface (Pl. XIII, fig. 10. 11. 12, b) is a
little convex laterally, whilst, the inferior surface is slightly
concave. Both the superior and inferior surfaces are
furnished, with an articulatory surface, articulating with the
corresponding surface of the superior and inferior
ambulacral plates. In this manner, the column is produced.
The lateral prolongation is narrow, where it springs from
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
surface 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 interbrachial
spaces, and approach the first ambulacral plates of the
corresponding adjoining rays, not, however, quite butting
with these, but producing an obtuse angle, with it’s
concavity facing the oral opening. The ambulacral plates
diminish 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)
articulating with a corresponding hollow articulatory surface
on the superior (interior) adambulacral plate (Pl. XIII,
fig. 13, b). The inferior extremity is nearly truncate, and
upon it, is seen, the above mentioned, oblong, hollow
articulatory surface. This inferior extremity expands laterally,
and forms, as it were, two spherical prominences (Pl. XIII,
fig. 11, /). 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
articulatory surface, for the large, long calcareous needle
contributing to expand the translucent integument of the ventral
surface (Pl. XIII, fig. 2, d. 11, g. 13, c). A little above
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