l i
M
if
•f 5
I
u
. > ]
l i i
l î ]
i
I append a Table showing the chief variations in the proportions
of the spicules :—
Proportions of Spicules (in millim.).
Smooth
Acuate.
Tibiella (including
heads
aud their
diameter).
Fine
Acerate.
Mediterranean specimens of
'T. digitata, nigrescens, am- ■
bigua, mnggiana ...............
T. digitata, var., Kurrachee _
specimen ...........................
Do., Thursday and Alert Islands,
Torres Straits, specimens
(2) ...........................
Do., Prince of Wales Channel,
Torres Straits, specimen ... J
Do., Port Darwin (Australia)
specimens (2) ...................
•29 by
•Oil to -012
•21 by' -007
•19 by -0063
•25 by -0063
•3 by -0095
•23 to -25
by '0063
TO by -0042
about '228
by ’006
•22 by -0042
r -2 to -25 by
\ -006 to -0063
•18 to -2 by
•0016 to -0017
■14 by '002
about
•18 by -0015
■22 by -002
•18 to -19 by
•0021 to -0032
In tho present collection are some more or less fragmentary
specimens, and two which incrust crabs, all well preserved in spirit;
they are either broad, massive, about 25 millim. (I inch) thick, or incrusting,
1 to about 6 millim. thick. The surface is covered with more
or less closely-set ridges or monticular elevations, from I to 3 millim.
high. The colour is pale grey of different shades (a purple colour
in ono case being apparently derived from a purple sponge which
arrived in the same bottle of spirit). The sjiicules agree closely in
form with those of Mediterranean specimens; and the only notable
difference in proportion is th a t the diameter of the acuate is from
i to ^ less than th at of those specimens. The colour is paler than
in the Mediterranean forms; but these exhibit a wider range of
variation in this respect than is shown by a comparison of the
darkest Australian and palest Mediterranean specimen. Therefore
I feel fully justified in uniting the two groups of forms as one
species, remarkable for its wide geographical distribution, polymorphic
external habit, and great range of spicular variation.
Hab. Alert and Thursday Islands, and Prince of Wales Channel,
Torres Straits, 3 -9 fms.; Port Darwin, between tide-marks.
Distribution. Mediterranean (Schmidt) ; Atlantic (Schmidt) ;
Antigua (Carter); Kurrachee (coll. Brit. Mus.).
T. increscens, Schmidt, JB. Comm. Unters. deutsch. Meer. ii.-iii.
p. 115 (off S.W. Norway), differs from these and all described
species in having a spinulate head to most of the smooth acuates.
DESM ACIDINIDÆ (Schmidt, 1870).
If all those sponges which contain hooked or bow-like flesh-
spicules were, in accordance with Vosmaer’s views, as expressed
m his very useful Revision (Notes Roy. Mus. Netherl. ii. p. 99),
included iu this family, it would not only bo the largest, in all probability,
of the families of Siliceous Sponges, but it would leave
some of the remaining ones mere skeletons. Judged by the facts
now known, the boundary region between the Desmacidinidæ and
Chalinidae is now narrow, but uot in reality so narrow as it would
be if the above definition is insisted on. Whatever may be tho
atfinities oî Homceodictya, ivith its anchorate flesh-spicules (referred
by 'Mr. Carter to the Chalinidæ), those of Toxochalina, mihi (see
Chalinidæ, supra), are undoubtedly with th at group; yet it has
a how-hke flesh-spicule in conjunction with a Chalinid acerate
skeleton-spiciile, horny fibre, and digitate habit. Until the homologies
of the flesh-spicules are better understood than they are at
present, I believe th at cases such as those ju st mentioned will
have to be considered separately on their individual merits as they
arise, having special regard to the direction in which the greater
assemblage of affinities point. I t seems probable th at this family
will only prove a fresh illustration of the maxim “ Natura non
facit saltum.” Besides Toxochalina I here exclude from the family
those genera (e. g. Clathria, Acarnus, Echinonema) in whieh any
of the spicules project laterally from the fibre ; such forms as these
seem to pass by gradations (Echinodictyum, Raspailia) almost into
Axinella and Phacellia, by losing, in the first case, the flesh-
spicule/ and in the second (Axinella &c.) the spined echinating
cylindricals. Rhizochcdina, on the other hand, seems linked to the
family by its occasionally horny fibres, and by its ally Oceanapia
with its bihamate flesh-spicule ; and I have ranged it (although only
provisionally) here as a degraded Desmacidine. I t probably owes
its peculiar form to its mud-loving habits. Two new generic types,
Gelliodes and lotrochota, are described below. ’
RHIZOCHALINA.
Schmidt, Atl. Geb. p. 35.
Phloeodictyon, Garter, Ann. S; Mag. Nat. Hist. 1882, x. p. 122.
This form is so aberrant in its coarser anatomy th at I think there
can be little doubt th at Carter has done right (I. c.) in making it the type
of a distinct group, although we have as yet no satisfactory information
about the arrangement and structure of the soft parts. Although I
can see no snfficient reason why the name Oceanapia, Norman, should
give way to the above names for such species as Desmacidon jeffreysi,
Bowerbank, whose spiculation includes a bihamate, yet 'it seems’
not undesirable to retain the older of the two for those which have
simply an acerate spicule. With regard to the question of syste-
2 E 2
I '