inatic position, which Carter ( I.e.) is inclined to regard as among
the Renierid®, I notice th at lihizochalina olerácea, at any rate, has
a true Chalinid fibre ; hut Bowerbank’s and Carters species never
approach this condition more closely than by producing a few
scattered compact fibres, wholly composed of spicules, like those of
some Fachychalinai; but the greater part of the organization is
Reuierid, and it appears to approach Schmidtia, Balsamo-Crevelli.
On the otlier hand, Oceanaqna, which seems to be nearly allied, has
the bihamate spicule. Taking this fact in conjunction with the
horny fibre of IHi. olerácea, it seems to me best to place the two
genera in the Besmacidiuida?.
54. Rhizochalina fistulosa, Bowerhank, var. infradensata, nov.
? A lc y o n ium p u t r id o s u m , Lanmrck, Mém. Mus. Hist. Nat. i. p. 168.
D e sm a c id o n f is tu lo s a , Bowerbank, P. Z. S. 1873, p. 19, p i. iv . figs. 7, 8.
Two more or less imperfect specimens in spirit, the largest about
25 millim. (1 inch) across tho body, and some detached dry tubes.
An arrangement here found, which 1 have not seen described in
this species, is th at of a dense layer of the skeleton-spicules, packed
side by side, at right angles to and about -25 to -8 millim. below the
surface of the sponge—below, th at is to say, the superficial Isodictyal,
or rather Halichondrioid (in Bowerbank’s sense) network containing
the subcortical crypts and other cavities. This layer recalls the vertical
layer of small suhspinnlates of liinalda uberrima, Schmidt, only
th at it is not, as there, placed at the surface. I t is represented in
the type specimen of the species by a layer in which the spicules are
set obliquely to the surface at various angles. As both the present
specimens present this peculiarity, I think it well to establish for
them a distinct variety.
One of the specimens exhibits the small crateriform eminences
figured on the outside of Bowerbank’s specimen, but the other does
not ; hence they probably have no systematic, and but little physiological
importance. The spicules agree closely in proportions with
those of the type.
Arafura Sea, Arafura Sea,
Type specimen. Spec. no. 1. Spec. no. 2.
Acerate spicule. . -27 by -011 to -0127 -25 by -Oil -25 by -012 mm.
Hah. Arafura Sea, N.W. coast of Australia, 32-36 fms. ; bottom
mud, sand, and shells.
Distribution. Fremantle, W. Australia (Bowerhank) (the typical
form).
The dermal membrane of one of the specimens contains a large
number of smooth acerate spicules of about half the length and
breadth of the proper spicules ; they do not occur below the membrane,
nor, apparently, in the other specimen. A similar circumstance
occurs in B. singaporensis described below ; in that case a
number of short blunt cylindrical spicules occur of the normal, or
almost the normal thickness, but only one half to two thirds the
length of the adult form.
55. Rhizóchalina singaporensis, Carter, var. ( P l a t e XLI. fig. s.)
Phloeoffictyon singaporense, Carter, Ann. 8f Mac/. N. H (1883) xii.
p. 326, pi. xiii. tig. 17. . V /
M ith this species I identify a series of specimens which usually
have the outward habit of B. fistulosa, but in which a large proportion
of the (usually acerate) spicules have both ends more or less
rounded. In the most perfect specimen the cortex is glabrous,
chestnut to purplish-brown in colour, thin ; the fistula? are wanting
on one, presumably the lower, surface. A smaller specimen consists
ot a barrel-shaped mass adherent by its lower surface to two other
sponges, and giving off from one latcr.il extremity one, from the
other two fiGula? and no others. A detached fistula exhibits
turcation, dividing into two unequal branches a t an angle of about
30 to each other. In one remarkable specimen the central p art of
the body is dongate, slightly compressed, and measures 110 millim.
(4-3 inches) in its present length, while its diameter does not exceed
12 millim. anywhere; in its other characters it agrees well with
the above specimens. A fragment of the bulbous part of a large
specimen shows th at part of this specimen, when perfect, to have
possessed a diameter of about 75 millim. (3 inches).
The ends of the spicules show almost every stage between a
merely blunted point and a rounded end like that of the base of an
ordinary acuate spicule : some thin, completely acerate forms, which
occur mixed with the blunt forms in the subcortical tissues, are
perhaps the young of the latter, indicating the typical shape from
which the adult spicules have diverged. The largest adult spicules
have nearly the same size as the acerates of the typical form of
R. fistulosa, viz. -3 by '0127 millim., hut they vary immensely in
length; the thin acerates measure -28 by -004 millim. In Carter’s
specimen the acerates measure -3 by -017, the blunt forms -04--08
by '004 millim.
Three fistula? retain their ends, and these are finger-like and
closed.
Hah. Prince of Wales Channel, West and Alert Islands, Torres
Straits, 7 fms.
Distrihution. Singapore (Carter).
I may explain th at I had at first distinguished this form as a
variety A R. fistulosa; bnt as Mr. Carter has, since then, published
a description of it as a distinct species, and as I had alreafly felt
th a t it should perhaps be so described, I assign the name proposed
by him to the Australian specimens.
56. Rhizochalina spathulifera.
( P l a t e XXXIX. fig. E ; P l a t e XLI. fig. q.)
Main body elongated, flexuous, cylindrical or somewhat compressed,
12-17 millim. in greatest diameter. External portion (cortex) in dry
state even, hard and dense on tho stem, where it is about '7 millim.
thick; rather uneven, porous and compressible on the branches;
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