synes at være ligeligt fordelte overalt, naar Dyret lever og 
er i fuld Vigør, Fig. 12. 'De ligge, naar Kroppen er ud- 
spendt, et ganske lidet Stykke fra hverandre, men nærme 
sig under Kontraktionerne; er Huden stærkt sammentruk- 
ken, hvilket i Regelen er Tilfældet, naar Dyret har været 
opbevaret i Spiritus, saa ligge Hjulene lagvis paa hver- 
andre; Huden faar da et sølvglindsende Udseende og føles 
haard. 
De store Hjul, Fig. 12, a, ere i størst Mængde til- 
stede, ere sammensatte af en Centraldel, der er flad, glat, 
og hvorfra udgaa Radier, hvis Antal varierer noget fra 
8—11; men hyppigst er der dog 8. Disse Radier have en 
vingeformig Udvidning, Fig. 13, a, der er bredest paa Mid- 
ten, hvorved de trekantede Mellemrum blive betydelig ind- 
knebne i den indre Halvdel, Fig. 13, 0. Peripherien er 
sammensat af saamange Stykker, som der er Radier, og 
fra hvert saadant Stykkes ydre Rand udgaar en lang Tand, 
der er bred ved sit Udsprmg, men ender temmelig spids, 
Fig. 13, c. Tanden har en Retning udad og nedad. Hju- 
lets Peripheri er saaledes besat med et Antal Tænder, der 
svarer til Radiernes Antal, og disse Tænder vende indad i 
Huden. Hjulet er paa Grund af Tændernes Stilling kon- 
kavt paa dets indre Flade, imedens dets ydre er plan. 
Disse Hjul variere lidt i Størrelse; saaledes er Tverdiame- 
teren fra Peripheriens ydre Rand paa den ene Side til det 
tilsvarende Punkt paa den anden Side fra 0.220—0.2907m; 
Tverdiameteren med Tænderne udgjør fra 0.820—0.350"”, 
Tændernes Længde 0.0807", 
De smaa Hjul ligge hist og her spredte imellem de 
store, Fig. 12, og ere meget forskjellige fra disse. De 
sidde paa en kort Stilk, lig dem hos Myriotrochus Rinkii. 
Centraldelen (Umbonen) er saagodtsom plan, men har en 
rund Knop paa Midten, hvortil Stilken er fæstet, Fig. 14. 
Fra Centrum udgaa i Regelen 11 Straaler, der ligeledes 
har en vingeformig Udvidning, Fig. 14, a, der ikke er saa 
bred, som paa de store Hjul, men som er tilstrækkelig til 
at give Mellemrummene et eget Udseende, Fig. 14, 0. 
Hjulets Peripheri bestaar af ligesaa mange Stykker, som 
Radiernes Antal udgjør. Fra hvert Stykkes indre Rand 
udgaa i Regelen 2 korte, trekantede Tænder, Fig. 14, c. 
Disse Hjul ligne meget Kalkhjulene hos Myriotrochus, Rin- 
kv; men Forskjellen er dog iøinespringende, idet Radierne 
ere noget anderledes byggede, og Tænderne ere baade kor- 
tere og i omtrent dobbelt saa stort Antal tilstede som hos 
Rinkii; hos begge er den ydre Flade skaalformig. Ogsaa 
disse Hjul variere noget i Størrelse, fra 0.071—0.098” i 
Tversnit. Tænderne ere 0.013”” lange. Hos Myriotrochus 
vare Hjulene 0.2337” i Tversnit; Tænderne 0.0497” lange. 
of as many segments as there are radii. 
and in such manner: as, it: would seem, to be equally di- 
stributed, so long as the animal is alive and in a perfectly 
healthy state, fig. 12. When the body is expanded, a mi- 
nute space intervenes between them, but on its contraction, 
they approximate; if the skin is much shrunk, which is 
generally the case after the animal has been preserved some 
time in spirits, these spicules lie one above the other in 
layers; the skin then acquires a glittering, argenteous ap- 
pearance, and is hard to the touch. 
The large wheel-shaped spicules, flg. 12, a, are the most 
numerous; they consist of a central portion, which is flat, 
smooth, and from which issue radii, varying in number from 8 to 
11; most frequently, however, there are 8. These radii, or 
spokes, have a pinnated expansion, fig. 13, a, broadest in the 
middle, and thus reducing in extent the inner half of thé 
triangular interstices, fig. 13, 6. The periphery is composed 
of as many segments as there are radi, and from the outer 
margin of each segment projects a long denticle, broad at its 
origin, but terminating in a comparatively sharp point, fig. 
13,¢. The denticles are directed outwards and downwards. 
The periphery has accordingly a number of denticles cor- 
responding with the number of its radi, and these den- 
ticles extend inwards mto the skin. From the position of 
the denticles, the mner surface of the spicule is concave; 
the outer: surface is plane. These large wheel-shaped 
spicules vary somewhat in size; the transverse diameter, 
measured from the outer margin of the periphery on 
one side to the corresponding point on the other, is 
from 0,.220”” to 0.290”"; the transverse diameter, including 
the denticles, ranges from 0.320”” to 0.8507”, The length 
of the denticles is 0.0807”, 
The small wheel-shaped spicules le scattered here and 
there among the large ones, fig. 12, from which they differ ma- 
terially in form. They are attached to a short stem, as in 
Myriotrochus Rinku. The gentral portion (umbo) is almost 
flat, but furnished in the middle with a round knob, to 
which the stem is webbed, fig. 14. From the centre pro- 
ceed, as a rule, 11 rays, likewise with pinnate expansions,’ 
fig. 14, a, not so broad as that in the large spicules, 
but of sufficient size to change the appearance of the inter- 
stices, fig. 14, b, The periphery of the spicules consists 
From the inner 
margin of each segment project as a rule 2 short triangular 
denticles, fig. 14, c. These spicules present considerable 
resemblance to the wheel-shaped spicules in Myriotrochus 
Rinkii, but are readily distinguished from the latter, 
having a somewhat different structure; the denticles,, too, 
are shorter, and their number about twice as great as in 
Rinkii; in both species the outer surface is cup-shaped. 
These smaller spicules, too, vary somewhat in size, their 
transverse diameter ranging from 0.071.”” to 0.098”. The 
In Myriotrochus, the 
the length 
denticles measure 0.0137” in length. 
999, 
transverse diameter of the spicules was 0.233””, 
of the denticles 0.049””. 
