'Alert' 1881-2

130 COLLECTIONS FROM MELANESIA.
determine to some extent its range of variation : this, as we might
have expected, is most markedly presented by the characters of the
spinous protuberances formed by the hypertrophy of some of the
granules on the abactinal surface ; the smallest specimen is without
any special spines. Of three larger and subequal specimens, that
which is a little the smallest has a more prominent granule developed
here and there along the middle lines of the rays, and some
six, still more prominent, at the centre of the dislv ; the other two
have much more prominent spinous granules at what may be called
the base of the rays, and some smaller protuberances around the
centre of the disk ; these latter are, in the largest specimen of all,
quite inconspicuous. E. is about equal to 2 r; R=72, 58 ; r—34, 27.
Arms 29 or 26 millim. wide at the base, narrowing hardly at all
marginal plates very well developed, equal
till quite near their end ;
in either series, and 13 or 14 in number ; pedicellarise scarce.
The central region of the disk is not distinctly elevated ; with
increase in size the ossicles of the abactinal surface become less
closely packed than in the smaller forms ; and three rows of ossicles
can be quite distinctly made out ; the investing granulation is not
especially coarse ; the intervening pores may be set singly or disposed
in groups of three or four. With increase in size, likewise,
the boundary line between the two sets of marginal plates becomes
more distinct ; from the angle of the arm outwards the superomarginals
increase in breadth till the last two or three, but they are
always at least twice as long as they are broad ; the terminal two
or three touch in the middle line. The infero-marginals are a little
stouter, but have otherwise much the same proj)ortions as the upper
series.
The intermediate plates are distinct from one another and are
covered by large distinct granules. The innermost row of adambulacral
spines are 6 or 7 in number, and are more delicate than the two
stouter ones which are placed outside them ; those of the outermost
row are smaller and more irregular, and are not easily distinguished
from the granules of the ventral plates.
Madreporic plate rather large, distinct, g to ^ r distant from the
centre ; the anus often distinguished by its periphery of eight or
ten small plates.
The dried specimens are yellowish or light slate-coloured ; but
there is no information as to what is their colour when alive or
fresh.
The species is verj-^ distinct from P. dilafatiis of Perrier, which
species has perhaps been founded on forms which were only varieties
of the Astrof/onium miliare of Gray.
Thursday Island, Torres Straits, 3-5 fms. ; sand.
19. Dorigona longimana.
Pentagonaster longimanus, Perrier, p. 228.
Percy Island, Queensland ;
7 fms.
Prince of Wales Channel, Aug. 1881,