'Alert' 1881-2

126 COLLECTIONS FROM MELANESIA.
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. R=67, r=9, or Il=7'5 r about. Adambulacral
spines flattened, 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 siirface 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,
madrcporic plate. The pore-areas are about 2 milhm. wide,
and the length of the madreporic plate, around which the granules
are very distinct, may be -1 millim. The colour of the abactinal sur-
face is deep brown or black, whilst that of the actinal surface is
lighter.
In a specimen smaller than that which has formed the chief basis
of this description the two surfaces arc, 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 that 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— («) one in which the
ossicles are so stout that no defensive spines are needed in addition
(h) one in which growth has proceeded so rapidly that the bars of
* Cf. Ann. & Mag. N. H. (5) viii. p. 441.
;