390 COLLECTIONS EKOM MELANESIA.
Main skeleton forming rectangular meshes; primary fibres strong,
running at right angles to surface, exhibiting horny margins (which
may form as much as one third of total thickness of fibre), about
•28 to ‘35 millim. apart, •! to ‘18 millim. thick. Secondary fibres
vertical to primaries, at about the same intervals, either without
foreign bodies or with ouly about half to two thirds of the thickness
occupied by th em ; in the former case -035 to -043 millim. thick, in
the latter '053 to •! millim. thick. Longitudinal fibres (primary of
Marshall) of same structure as primaries, hut less horny, -18 to -28
millim. apart, -14 to '21 millim. thick, running upwards and spreading
out somewhat from each other. Dermal skeleton composed of
long compound fibres, the primaries running parallel to each other
and to the long axis of the sponge, -Bo to -43 millim. a p a r t; the
secondaries extended between them at considerable intervals; primaries
-14 to -28 millim. broad, secondaries -1 to -14 millim., the
horny matter of the former usually, of the latter often, obscured by
the foreign bodies, which often project much from the fibre. Horny
substance amber-yellow. Sarcode amber-yellow, transparent.
Foreign bodies of fibres small, chiefly sand.
Hah. North-east coast of Australia.
The single specimen is 105 millim. (44 inches) high by 65 millim.
greatest width. In its even compact surface it differs from all other
Dysiclece except i l . / a i ’osa. Marshal], with which it also agrees in
the large development of the tnbnlar form which it exhibits. The
strongly horny character of the secondary fibre, however, distinguishes
it from this (as from most, if not all other) species, and
allies it to Hircinia. These striking characters, and the good preservation
of the specimen, seem to warrant its description.
18. Psammopemma densum, Alarshull, var. suhfihrosa.
( P l a t e X L I . f ig . A.)
Psammopemma densum, Alarshall, Zeitsch. iciss. Zool. xxxv. p. 113.
Agreeing closely in size and external characters with Marshall’s
account of this strange form is a specimen in spirit in the present
collection. I t has the size and almost the shape of a horse-bean,
and is of a grey colour. The dermal membrane contains numerous
foreign bodies, but is in parts transparent, though fibrillatcd. Owing
to an inferior amount of contained sand, a distinct network of wholly
sandy fibres is to bemade out, which Marshall did not find in his specimens
; the meshes are round, about -3 miUim. in diameter, in the
natural state almost filled np with sarcode containing foreign bodies.
Sarcode very pale brown, suhtransparent. The radiating tubes indicated
iu Marshall’s figure (6) appear to me possibly to represent
spaces between primaryfibres; but those fibres in the present specimen
are not straight, but bend right and left to meet the short secondary
lines ; thus a vertical section of the sponge exhibits a somewhat
honeycomh-like appearance. No trace of horny matter was observed.
Hah. Thursday Island, Torres Straits, 3-4 fms.
Distrihufion. Tasmania (Marshall).
SPONGIIDA. 391
APLYSINIDÆ.
Aplysinida, Carter, Ann. Sj Mag. N. H. (5) xvi. p. 132.
This name is used in a wider sense than th at to which Vosmaer
(Mitth. Zool. Neapel, iv. p. 444) limits it.
19. Aplysina inemhranosa.
Spongia membranosa, Pallas, Elench. Zooph. p. 398.
Spongia membranacea, Esper, Pflanzenth. ii. p. 256, pi. xx.xiv.
? lanthella concentrica, Hyatt, Mem. Bost. Soc. ii. p. 407.
? Aplysina purpurea, Carter, Ann. V Alag. N. 11. (5) vi. p. 36.
A very fine species, fortunately preserved in spirit as well as in the
dry state. I t forms a cylindrical mass, which has the same general
form as th at given in Fsper’a figure (I. c.) ; the base of the wot
specimen is about 40 millim. ( l |iu c h ) in diameter. The dry specimen,
which is much the largest of the two, is 580 millim. (2 2 | inches)
high, and the maximum diameter, which is at about 5 inches above
the base, is about 40 millim. ( I f inch). At 77 millim. (3 inches)
above the base a branch is given off, 22 millim. ( | inch) in maximum
diameter and 145 millim. ( 9 | inches) in length, and on the same
side, about 30 millim. higher up, a smaller branch, 12 millim.
( I inch) in maximum diameter and 75 millim. (3 inches) in height.
Ih e skeleton consists of a very open and irregular network of fibres,
1-5 to 2 millim. in thickness, xvhich arise at the base of the sponge,
and take a longitudinal but somewhat sinuous course along the interior
of the cylindrical column of which the sponge consists. They
throw out branches somewhat freely from their sides, aud subdivide
terminally into ramifying branches ; the resulting twigs anastomose
freely, the superficial ones end in outwardly and upwardly directed
points, usually hi- or tri-fnrcate, which are ju s t covered by the
tough dermis; the apices are -18 to -28 millim. in diameter. The
dermis and the internal membranes consist of a tough membrane
of a puce or dull purple colour in spirit, almost black iu the dry state.
The membrane is seen with the naked eye to be marked with numerous
raised thickened lines, which radiate from the projecting apices
of the dermal conuli (formed by the tension of the dermis over the
points of tho skeleton, as mentioned above), and branch and anastomose
on the membranes. Under the micro.scope they are seen not to
be special fibre-structures, but to consist simply of thickened membrane.
The membrane is coloured by purplish cells, which are about
•03 millim. in diameter, and are crowded with semiopaque granules,
to^ which they owe their colour. The fibres of the skeleton have a
wide central cavity, occupying about half their diameter, and filled,
or almost so, with a transparent substance coloured diffusely of a
purplish-red colour. The walls of the fibre are composed of laminæ
which separate readily, and may then be seen to consist of a dark
substance, rather readily torn, thickly set with fine dark pnrple-red
1 3;1
!^ I
^V ;1 • i i ■ '
: ! :
; i ' if;
'te îi;'
5 ^ i';';
teli'
II!