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432 COLLECTIONS FROM MELANESIA.
the Indo-Pacific region, agrees well with the typical form of the
genus, only presenting its peculiarities, both external and internal,
under a decidedly more striking form than in the Atlantic and
Mediterranean species. Halichondria infrequens, Carter, differs from
it in having tlie spined acerate skeleton-spicnle which occurs iu
some of the Atlantic species, hut agrees with it in having a bihamate
; its external characters are unknown, but it will almost
certainly prove to be a Crella.
66. Crella schmidti. ( P l a t e XL I. fig. a a.)
Massive, sending up moderately thick lobes pierced by passages
1 to 4 millim. in diameter, lined by smooth surfaces bearing the
pores. General surface covered with narrow longitudinal ridges
about 1 millim. broad, 5 millim. high, and 1 millim. apart, rough ;
dermal membrane between ridges smooth, transparent. Yents few,_
in depressions 1 to 3 millim. deep. Texture in spirit like crumb ot
bread ; colour dirty yellowish white. Main skeleton somewhat irregular,’
spiculo-fibre devoid of horuy matter ; in deep parts spicules
1- or 2-serial, fibres very irregular in direction; towards the periphery
primary fibres, with spicules 2- to 4-serial, run towards the surface,
generally at an obtuse angle to it ; they terminate between the
intermarginal chambers in tufts of the tibiella spicule, 12 to lo
spicules broad, the distal ends of the tihiellæ spreading out upon the
dermal membrane and forming its only skeleton. Sarcode pale
brown, rather granular. Spicules :—(1) Skeleton acerate, smooth,
straight or slightly curved, tapering to sharp points from near
centre; size -22 by -0063 millim. (2) Tibiella of dermal tufts,
straight, smooth, heads of same thickness as centre of shaft ; shaft
tapering to necks below heads, necks tapering gradually to the oval
heads ; size -22 by -0063 millim. (3) Equianchorate of flesh, tridentate,
the shaft stout, strongly curved ; the teeth strong, well
curved inwards, sharp, the two lateral ones united to shaft by falcate
expansions ; length of spicule '037 millim., th a t of each head -013
millim., thickness of shaft -0044 millim. [(4) Bihamate of flesh,
contort, curve moderate, ends bent sharply inwards ; size -037 by
•0021 millim. Possibly foreign to the sponge, but not uncommon
in both the deeper and superficial parts of the sarcode.]
Hah. Port Jackson, 0 -5 fms.
The only specimen is in spirit and well preserved, but small ;
the external characters peculiar to the genus are, however, well
marked. Whereas the head of the tibiella is scarcely defined as
such in any of Schmidt’s species (of which two are from the Adriatic
and two from the West-Indian seas), here it is quite a stiiking
feature of the dermal membrane when seen in section; in Haliclion-
dria infrequens, Carter, above referred to, the head of the tibiella is
similarly well defined. The spicules are generally stouter than
those of Schmidt’s species, and none of the skeleton forms are spined,
as appears to he the case in C. elegans and papillosa, if not in hospi-
talis. I associate this species with the name of the distinguished
>t !
SPONGIIDA. 433
spongofegist to whose keen eye for generic characters we owe this
very distinct and constant genus. k 1.,^
lOTROCHOTA *, g. n.
Halichondria, pars, Higgin, Bowerhank, Carter.
_ Desmacidinidæ with smooth linear skeleton-spicules and minute
birotulate flesh-spicules with straight shafts, both the heads being of
the same size, circular, and symmetrical ; sarcode purple.
This genus is formed to include Ilalichondria hirotidata, Higgin
(Ann. & Mag. Nat. Hist. 1877, xix. p. 296) and Halichondria p u r -
qmrea, Bowerbank_ (P. Z. S. 1875, p. 293). Halichondria s. str. is
based on a llenierid. The peculiar flesh-spicule of this genus is one
form of the flesh-spicule which usually appears in the Desmacidinidæ
under the form of an “ anchorate,” equi- or inequi-anchorate.
The latter forms apparently originate by excentric flexion of the
shaft ot a birotulate form like the present, and suppression of the
rays which lie on th at side towards which the shaft is bent ; the thin
expansions uniting the arms in the birotulate apparently become
the “ falces ” which unite the arms of the anchorate (see Carter,
Ann. & Mag. Xat. Hist. 1874, xiv. p. 207). An intermediate stage
is seen in Ghrondrocladia—viz. C. virgata, Wyville Thomson, and
C. {Halichondria) ahyssi. Carter (Yosmaer),—the shaft of the birotulate
being bent and the arm of th at side almost aborted as in a normal
anchorate (see Carter, tom. cit. p. 218). Chondrocladia differs further
ixom. lotrochota in being accompanied by a bihamate or tricurvate
flesh-spicule. Cladorrhiza, Sars {C. abyssicola, id. Some Remark.
Eorms &c. i. p. 65, pi. vi. figs. 16-34), is an allied form, but not
only has the shaft of the birotulate bent, and the symmetry of the
head impaired by the almost total reduction of that arm of the head
which thus comes into contact with the curve of the shaft, but it is
inequi-hirotulate, aud corresponds in the birotulate series to the in-
equianchorate form of the anchorates of the common types of Desmacidinidæ
; it differs from lotrochota in the possession of a bihamate
flesh-spicule in addition to the birotulate.
I t is noteworthy th a t those species of this genus hitherto known
are from shallow water (littoral, see below), while all other known
allied forms except Axos anchorata, Carter, for which the depth is
not given, are from the deep sea.
Erom an unusually well-preserved specimen of the green variety
of I . purpurea from, the Amirante Islands (see Pt, I I . of this Report),
I am able to make out th at the ciliated chambers are oval, the ends
being well rounded, and measure -032 by -025 millim. They are
crowded along the sides and in the parenchyma, lying between what
appear to be secondary and tertiary canals of the excretory system,
and also (though this may perhaps be merely apparent) upon the
* From lov, a violet, and rpo^os, a wheel, in allusion to the purple colour and
the birotulate flesh-spicules.