i
8. Linckia pauciforis.
Martens, Arch. f . Nat. xxxii. (1866), p. 69.
In only one example is one of the arms otherwise than perfect ;
but this does not seem to have been budded out in place of one cast
off, but to have been bitten or broken off not far from its tip.
Three dry specimens from Bird Island, N.E. Australia ; coral-
reef.
9. Linckia megaloplax.
Arms five. K = 6 7 , r = 9 , or 11=7-5 r about. Adamhulacral
spines battened, one for each plate, with blunted end ; externally
to and alternating with these are somewhat shorter papilliform
spines ; the general granulation of the actinal surface of the disk
extends between these latter ; externally to them there is a row of
larger spines, the distribution of which is extremely irregular, for
while at some points they are almost as closely packed as those of
the more internal row, they are at others separated from one
another by the distance of three or four of the inner spines. The
rest of the abactinal surface is closely covered with subequal granules
of some size. The abactinal surface is traversed very regularly
by six rows of poriferous spaces, which are comparatively
large and markedly rectangular ; the smallest spaces are found in
the lowest row on either side ; a short distance from the tip of each
arm the spaces completely disappear, and the granulation becomes
a little more prominent, and there is here, as in some allied species,
a large specially modified plate with one or more large tubercles
upon it. The disk itself is covered with large pore-areas, and the
only noticeable character is the large and distinct, though not projecting,
madreporic plate. Tho pore-areas are about 2 milhm. wide,
and the length of the madreporic plate, around which the granules
are very distinct, may be 4 millim. The colour of the ahactinal surface
is deep brown or black, whilst th at of the actinal surface is
lighter.
In a specimen smaller than th at which has formed the chief basis
of this description the two surfaces aro, towards the free end of the
arm, distinguished from one another by the development of some
short marginal spines. In another, dried, specimen, intermediate
in size between these two, the spines at the upper and lower margins
of the sides of the arm, though insignificant, are both larger
and more numerous.
The idea th at the younger forms would have a larger supply of
spines is opposed by the fact that in a still smaller specimen these
spines are altogether absent*, while the skeletal plates are stouter
than in the specimens which bear the spines. The question now
arises as to whether there are three stages—(a) one in which the
ossicles are so stout th at no defensive spines are needed in addition ;
(b) one in which growth has proceeded so rapidly th at the bars of
* Cf. Ann. & Mag. N. H. (5) viii. p. 441.
the ossicles have diminished in proportional thickness while in creasing
in length, and so having lost their earlier stoutness, now
require external a id ; and (c) a final condition, in which equilibrium
is again established, the ossicles themselves being again stouter,—or
whether we have to do with two sets of variations from a common
stock, due to some slight differences in the environment. But this
is a complex aud difficult question, which can ouly be satisfactorily
answered by one who has a t hand the living wealth of the Australian
seas.
Port Curtis; Eitzroy Isla n d ; Albany Is la n d ; Port Denison,
8-12 fms.
10. Linckia, sp.
A very small specimen, from AVest Island, Torres Strait, presents
that interesting peculiarity of three smaller and three larger arms,
hinting thereby at a division of the disk instead of gemmation from
a single arm ; it is the smallest heteractiuic Linckia I have seen, the
longest arm measuring only 6 millim.
11. Anthenea flavescens.
Perrier, p. 276.
Port Jackson, 0 -5 fms.
The Museum collection contains also specimens of this species
from Eremantle, AV. Australia.
12. Oreaster gracilis.
Pentaceros gracilis, Perrier, p. 246.
Oreaster gracilis, Liitken, Vid. Med. 1871, pp. 260, 261.
A selected series of five specimens, all from Port Denison (4 fms.),
exhibit remarkably well the great change which occurs in this
species, even after a considerable size has been attained. The
smallest, which has B equal to 93-5 millim., has five tubercles,
about 10 millim. high, one at the central end of each median row
of tubercles ; in another, with B equal to 108 millim., the
tubercles, though a little stronger, are no higher and are here only
to be found on three of the angles of the disk ; this specimen, like
another which is a little larger, has the lateral and marginal spines
very well developed : two specimens, with B equal to 118 and
140 millim. respectively, have these spines less well developed, and
the diminution is the more marked in the larger specimen ; the
smaller has one large central tubercle, and the larger has each of
the whole set of five reduced to growths which are hardly larger
than the other spines on the disk.
A specimen with six arms, one of which has been injured and
has commenced to grow again, was collected at Port Molle.
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