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28
og sparsomme. Basaldelen er meget bred, danner paa sin
nederste Rand en lige Linie; den øverste Rand er
afrundet, og Siderandene have et lidet Indsnit, Fig. 7, a.
Kjæ-verne ere korte, men meget brede og danne paa deres
nederste Del en næsten spids Yinkel, Fig. 7, c, idet de
smalne af mod Leddefladen. Den øverste Ende er
afstumpet. Hele den ydre Flade dannes af et Kalknet, Fig. 7, b,
og paa de indre Rancle, især paa deres nederste Del, sees
stærke, fremragende Tænder, Fig. 7, d.
De korsformede Pedicellarier have en bred Basaldel
med meget fremstaaende Apophyser, Fig. 6, a. Tangens
Kjæver ere kun lidet bøiede, og hele den ydre Flade er
langs Midten forsynet med Vacuoler, Fig. 6, b, imedens
den indre Flade, ligesom Randene, have stærke, spidse
Tænder, Fig. 6, c. Der, hvor Kjæven gaar over i den
forlængede Del (Tangens Arm), er en stærk Indskjæring,
Fig. 6, d, hvorefter Delen bliver meget bred og har paa
den afrundede Endes udvendige Flade en Samling af
Takker, Fig. 6, e.
Hudskelettet bestaar af større og mindre, forskjelligt
formede Kalkstykker, Fig. 8. Paa Skivens Ryg er en
temmelig stor, noget kantet Centralplade, Fig. 8, a, der
paa sin øvre Flade har flere smaa runde Ophøininger,
hvorpaa Pigge ere fæstede; lige ved Randen af Pladen,
just mod den Armvinkel, hvor Madreporpladen sidder, sees
den lidt aflange Analaabning, Fig. 8, b. Til
Centralpladen støde meget smaa, lidt aflange Kalkplader, Fig. 8, c,
der ordne sig i en Kreds omkring Centralpladen, og som
hvile, dels paa denne, dels paa hinanden indbyrdes, idet
de dog danne en lille Aabning imellem sig for et
Tentakelrør, Fig. 8, d.
Imellem hver Armvinkel sees en stor, noget
uregelmæssig Kalkplade, Fig. 8, e, til hvis indre Rand de
omtalte smaa Kalkplader føie sig, medens den ydre og
Siderandene er dækket af Plader fra Armene, Fig. 8, /. En
af disse Armvinkelplader indtages for endel af
Madreporpladen, Fig. 8, g, hvis indre Rand grændser nær til
Analaabningen.
Paa Armenes Ryg antage Pladerne Korsformen ’mere
eller mindre udviklet, ligesom de her danne regelmæssige
Længderækker, Fig. 8, h. Paa Midten af Armen er
Kors-formen stærkest udviklet, ligesom Pladerne her ere størst
og mere hvælvede, hvorved den førbeskrevne Kjøl
fremkommer, Fig. 8, i; til Siderne blive de noget mindre
og ere mere langstrakte; de hvile taglagte paa hverandre
og danne smaa Masker, der staa i Længderækker og
optage hver et Tentakelrør, Fig. 8, k. Alle Pladerne,
saavel de paa Skiven som paa Armene, have paa deres ydre
Flade flere eller færre smaa Knuder, hvortil Piggene
fæste sig.
few in number. Their basal part is very broad, and has
a straight inferior margin, whilst, the superior margin is
rounded off, and the lateral margins of the basal part are
slightly concave fig. 7, a). The jaws are so short in
proportion to their breadth, that the angle formed by the
junction of the lateral and inferior basal margin, is almost
acute (fig. 7, c). By contracting in breadth towards the
articulatory surface, lateral hollows are produced. The
points of the forceps are blunted. The entire exterior
surface is formed of a calcarous reticulation (fig. 7, b), and on
the interior margins, especially, of their basal portions,
strong prominent teeth are seen (fig. 7, d).
The cruciform pedicellariæ have* a broad basal part
with very prominent apophyses (fig. 6, a); the jaws of the
forceps are only slightly curved, and the whole of the
exterior surface is furnished with vacuola, which extend
along the mesial line (fig. 6, b), whilst, the interior surface,
as also, the margins, have strong acuminated teeth (fig. 6, c).
At the point where the jaw passes into the elongate
portion, (the forceps arm), there is a deep hollow (fig. 6, d),
beyond which, the part becomes very broad, and upon the
rounded extremities, the exterior surface is furnished with
I a collection of aculeæ (fig. 6, e).
The dermal skeleton consists, of larger or smaller
variously formed calcareous ossicles (fig. 8). On the abactinal
disk, there is a pretty large, somewhat angular, mesial
plate (fig. 8, a), having several, small, circular prominences
on its superior surface, to which spines are secured. Close
to the margin of this plate, and just opposite to the
in-terbrachial angle at which the madreporite is situated,- the
somewhat oblong anal aperture is seen (fig. 8, b).
Somewhat oblong, very small calcareous ossicles abut on this
mesial plate (fig. 8, c), and arrange themselves in a circle
around it, partly, resting upon it, and partly, reciprocally,
resting upon each other, but still, leaving a small
interspace for a tentacular tube (fig. 8, d).
Between each interbrachial angle, a large somewhat
irregular shaped calcareous plate (fig. 8, e) is visible; to
the inner margin of this, the small calcareous plates
already mentioned unite, whilst, its exterior and lateral
margins, are covered, by plates pertaining to the rays (fig. 8,/).
One of these interbrachial angle plates is partly included
by the madreporic plate (fig. 8, g) whose inner margin
extends nearly to the anal aperture.
On the abactinal surface of the rays, the plates
become, more or less distinctly cruciform, whilst, in this
situation, they also form regular longitudinal series (fig. 8, h).
The cruciform shape is most distinct in the middle part
of the ray, and here, also, the plates are largest and more
arcuate, producing thus, the previously described ridge
(fig. 8, i). On the lateral surface of the rays, the plates
are somewhat smaller, and more elongated; they rest
imbricate on each other, forming a longitudinal series of
small meshes, each of which receives a tentacular tube
(fig. 8,k). All the plates, pertaining to, both, the disk and
the rays, have, upon their exterior surface, a greater or smaller
number of small knobs, to which the spines- are secured.
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