6 fladtrykte Pigge, hvoraf de to midterste ere de længste 
og kunne betragtes som Tender; desforuden findes paa 
Underfladen, henimod den forreste Rand, to stærke, meget 
lange, runde Tender, en paa hver Side af Mundpladernes 
ophøiede Sutur, hvilke rage udover Mundaabningen, Fig. 8, d. 
Ryggens Hudskelet have vi tidligere omtalt. 
Bugens Hudskelet dannes af listeformige, flade Kalk- 
stykker, der ligesom Ribber, Fig. 4, a, udfylde Rummet 
imellem Bugfuren og Armens Rand. Disse Kalkstykker 
ere langstrakte, tykkere paa Midten, tyndere mod Randene 
og have en skraa Retning indenfra udad, ovenfra nedad. 
De ere taglagte saaledes, at den ovenforliggende Plades 
tynde Rand dækker lidt af den underliggendes. Fugerne 
ere tildels forkalkede, saa at man ogsaa her, nemlig paa 
Armenes Bugflade, har en Slags Pantserbekleedning. 
Den indre Ende af disse Kalkribber, Fig. 8, 0, stø- 
der umiddelbart til en Adambulacralplade, imedens den 
ydre frembyder en lidt ophøiet Ledflade, der artikulerer 
med de førbeskrevne Randpigges konkave Ledflade. Til 
denne ydre Ende, over dens Artikulationsflade, støde umid- 
delbart de smaa, aflange Sideplader af Armens Rygskelet, 
Fig. 4, c, hvilke kunne betragtes som dorsale Randplader, 
der ere placerede i en Række langs Armens Rand og 
kunne kun iagttages efter en meget omhyggelig Præpara- 
Enhver af disse Randplader bærer en Paxille, hvis 
Naale ere temmelig korte. Kalkribbernes indre Flade er 
glat og har paa Midten en ophøiet Længdelinie; den ydre 
Flade er noget mere ujevn og har paa Midten en rund, 
ophøiet Ledflade, der artikulerer med den tidligere be- 
tion. 
skrevne midterste Pig paa Armens Bugflade. 
Skelettet frembyder intet særdeles mærkeligt. Am- 
bulacralpladernes Tverprocessers ydre Del har en skefor- 
mig, konkav Flade, Fig. 4, d, der synes at være Fæste- 
punktet for en Muskel, som strækker sig hen over Ribber- 
nes indre Ende. Adambulacralpladerne ere smaa og flad- 
trykte, bære paa den mod Ambulaeralfuren vendende Rand 
to Pigge, der tidligere ere omtalte, og stode med sin indre 
Rand til Kalkribbernes indre Ende. 
Ocellerpladen er forholdsvis temmelig stor og har 
paa Midten en dyb Fure. 
Odontophoren er næsten firkantet, noget fladtrykt; 
den øverste Rand, der er kun lidet hvælvet, er noget bre- 
dere end den underste, der har et neppe mærkbart Ind- 
snit. Den ydre Flade, den som vender til Kropshulheden, 
har paa Midten en stærkt fremspringende Kam (Apophyse) ; 
til Siderne af denne er en svag Fordybning, Fig. 11. Den 
98 
margin, six flattened spines, of which, the two middle ones 
are the longest, and may be considered to be teeth. There 
is also found, on the interior surface towards the anterior 
margin, two very long, strong, round teeth, placed, one on 
each side of the oral plate’s elevated suture, and these 
project inwards, over the oral aperture (fig. 8, d). 
The abactinal 
spoken of. 
dermal skeleton has already been 
The actinal dermal skeleton consists of fillet-formed 
flat calcareous pieces, which like ribs (fig. 4, a), occupy 
the space between the actinal furrow and the margin of 
the ray. These calcareous ossicles are elongate, thick in 
the middle, and thinner towards the extremities, and have 
a direction, slanting from the interior part outwards, and 
from the superior part, downwards. They are imbricate, in 
such manner, that the thin margin of the superior plate 
covers a small part of the margin of the inferior plate. 
The joints are partly calcified, so that, also, in this situa- 
tion, we find a description of calcareous armour plating. 
The inner extremities of these calcareous ribs (fig. 
8, b), butt, immediately, to an adambulacral plate, whilst 
the outer extremity, presents a slightly elevated articulatory 
surface, which articulates jwith the previously described 
concave articulatory surface of the marginal spine. ‘To the 
outer extremity, above its articulatory surface, the small, 
oblong lateral plates of the dorsal skeleton of the ray 
closely butt (fig. 4,¢), and may be considered to be dorso- 
marginal plates, placed in a series along the margin of the 
ray; but, they can only be distinguished after a careful 
Each of these marginal plates car- 
ries a paxilla, whose needles are rather short. The inner 
surface of the calcareous ribs is smooth, and has an elev- 
ated longitudinal rib in the middle. The outer surface is 
somewhat more uneven, and has a round elevated articul- 
preparatory treatment. 
atory surface in the middle, which articulates with the 
previously described mesial spine on the actinal surface of 
the ray. 
The skeleton presents nothing particularly noteworthy. 
The exterior part of the transverse processes of the amb- 
ulacral plates, has a spoon-shaped concave surface (fig. 4, d), 
which appears to be the point of insertion for a muscle 
that extends out over the rib’s inner extremities. The ad- 
ambulacral plates are small, and flattened, and carry two 
spines on the margin facing the ambulacral furrow, 
which have already been spoken of, and they butt with 
their inner margin, to the inner extremity of the calcar- 
eous ribs. 
The ocular plate is, proportionally, rather large, and 
has a deep furrow in the middle. 
The odontophore is nearly square, and somewhat flat- 
tened. The superior margin, which is only slightly con- 
vex, is somewhat broader than the inferior margin, and on 
the latter, there is a scarcely perceptible incision. The 
exterior surface; the one facing the body cavity; has in the 
middle, a strongly prominent ridge (Apophysis). On each 
