i ' i l l H î ;;
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fibre. (4) Equianchorate ; navicular, shaft almost straight, pointed
at each end ; length ’OIG-'OIS millim.
JIab. Port Darwin, 7-12 fms. ; bottom sand, mud, and shells.
The above diagnosis is based on a large specimen. A small
specimen (which is perhaps the apex of a larger one), 36 millim.
high, also occurs from the same place and same depth, differing
from it in having no perceptible horny fibre, in being, in consequence,
soft aud flaccid, and in having the spined acuate confined to a
central axis which contains a largo quantity of sand ; it is probably
identical with the large specimen, its differences being partly in dividual,
partly due to youth ; it contains the parasite Spongio-
pliagiis, Carter. This very fine species appears to be referable to
Rhaphidophlus hy possessing a distinct dermal crust composed mainly
of smooth spinulate spicules with their points projected outwards,
but adds to this the presence in this crust of the spined echinating
spicules, a feature iu which it resembles Dirrhopalum. The crust
is thin, but appears to represent the correspondingly situated structure
in R. cratitius, Esper (Ehlers). Its root-like base recalls the
horizontal meshwork figured by Esper, and here, as there, the erect
portion appears to have no real tendency to form branches ; hut,
besides the differences in the dermis, the skeleton and echinating
spicules are both much longer than in the type and hitherto only
recognized species of the genus. The height of the perfect and
well-preserved spirit-specimen is 470 millim. (18-3- inches). The
arborescent form, the strongly horny fibre, tho slenderness of the
skeletal andUchinating spicules, the replacement of the spinulate
for the most part hy the spined acuate in the main-skeleton fibre,
and the thickness of the dermal crust, distinguish R . arborescens from
R . procerus.
81. Rhaphidophlus, sp.
The following appears to be distinct from aU known species of
the genus, hut more material is necessary for fuU description :—
A small dry specimen of subramose cylindrical growth, 45 miUim.
long by 12 millim. in greatest diameter, the surface proliferating
into ridges and processes 2 -3 millim. high, giving it a flocculent
appearance. Colour pale dusky brown. Skeleton irregularly rectangular
in arrangement ; spicules united in the fibre by a small
amount of very pale horny substance, which is only occasionally
seen outside the spicules ; primary fibres about 8 to 10, secondary
6 to 8 spicules broad. Dermal skeleton a single layer of smooth
suhspinnlates in tufts radiating outwards.
Spicules ;—(1) Smooth acuate, tapering gradually to sharp point;
size -23 hy -0095 to -0127 millim. : in fibre. (2) Smooth suh-
spinulate, forming dermal layer ; head very slight, larger than shaft ;
tapering gradually to sharp point; size -25 hy -0095 to -0127 millim.
(3) Spined cylindrical, tapering gradually from well-rounded, very
slightly dilated base to rounded apex, which is about one third
the diameter of the base; spines prominent, sharp, distal ones
strongly recúrvate ; size of sificule -07 by -0095 m illim .: very
abundant on the fibre. (4) Navicular equianchorate of sarcode,
shaft slender, almost straig h t; length of spicule -018 miUim.
Hab. Prince of Wales Channel, Torres Straits, 5 -7 fms
ACARNUS.
Oraij, P. Z. 8. 1867, p. 544.
^ Acarnia is used as a generic name in an earlier part {tom.
cit. p. 515) of the same paper as th at in which Dr. Gray described
Acarnus; but it has not come into general use, otherwise the
essential agreement in form between the two words would necessitate
the suppression, on th at ground, of the later one. A careful
comparison of the grapnel-spicule, which characterizes the genus,
with the spined cylindricals of Clathria and Echinodictyum shows
th a t the affinity of the sponge is with these genera rather than with
the “ Tethyadm” of Dr. Gray,as held by him, or with the “ Esperiadie,”
as supposed by Mr. Carter (Ann. & Mag. Nat. Hist. 1871. vii. p. 274).
A . innominatus. Gray* {I. c.), besides the remarkable 4-hooked
grapnel-like spicule and the acuate (not cylindrical, as stated by
Gray, I.e.) form which characterize the main skeleton, possesses—as I r - - — X., J ^ kj V./U O N./IJ CltO JL.
have been able to ascertain by an examination of a mounting made
by Dr. Bowerbank, who was the first to figure and describe these
spicules (Mon. Brit. Spong. i.figs. 73-76, 292), which Dr. Gray afterwards
embodied in his description of the species—also a tricurvate
(figured by Bowerbank) and an equianchorate flesh-spicule; the
former about -13 by -0042 millim. in dimensions, the latter -016 to
D24 millim. long ; also a tibiella, measuring about '28 by -0045
(shaft) or ‘0063 (head) millim.
82. Acarnus ternatus. ( P l a t e XL II. figs. b, V.)
Erom a mounting which the Museum owes to the liberality of Dr.
John Millar, and from the spirit-specimen in the present collection,
we learn th at in this new species the acuate spicules are imbedded
in a reticulate horny skeleton of a pale salmon-red colour, and not,
as usual, yellow. The grapnel has hut three hooks, and the tibiella
has the shaft only -003 millim. thick. The other spicules agree with
those of A . innominatus. The largest of the present specimens is
about 65 by 25 millim. ( 2 | inches by 1 inch), and forms a clathrous
structure of round soft anastomosing trabeeulæ which are about
3 millim. in diameter. Colour in spirit reddish brown. Several
specimens occur in the present collection.
Hab. West Island and Prince of Wales Channel, Torres Straits,
7 fms. ; bottom sand and coral.
Distrihution. Bombay? {coll. Brit. Mus.).
* Mr. Carter gives reasons {I. c.) for his supposition that the West Indies
are the home of _ this species; the specimen, however, to which he appeals in
support of this view, viz. that attached to the base of a specimen of the Westilf
'te,.- !
-iii i (I