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620 C O L L E C T IO N S F E O M T H E A V E S T E E N I N D I A N O C E A N .
50. Erylus cylindrigerus *.
( P l a t e L III. lig. M ; P l a t e LIV. figs, e-e""".)
Massive, suberect; terminating above in a lobate prolongation.
Surface smootb, slightly uneven. Agents ono (or more ?) near apox
of sponge, about 2 millim. iu diameter, opeiiiug flush witb surface,
leading obliquely and deeply doAviiAvards into sponge. Texture iu
spirit tough, firm, but somewhat flexible; colour in spirit dark
broAvn, almost black. Skeleton composed of bundles of spicule
no. 1, 6-8 spicules broad, radiating from centre to just below surface,
4 7 to ‘3 miUim. apart near surface. Surface covered witb a
layer about 4 millim. thick of tbe discoid spicule no. 2, arranged
borizontally. Sarcode subtransparcDt, very pale brown, almost
colourless.
Spicules:—(I) Zone-spicules subcylindrical, smooth, straight or
very slightly and gradually curved, tapering from Avitbiii about six
diameters of ends to rounded terminations of about ono tbird the
diameter of tbe middle of tbo s h a ft; size about •? by ‘032 millim.
(2) Discoid, of subdiamond-sbaped outline, viz. th at of a rhombus
witb tbe angles rounded off; length ’21 to '28 millim., breadth
4 to 4 4 millim., thickness about ‘04 millim.; covered Avitb minute
low pmictiform spines, about -012 millim. apart (spines, as seen
under a high power from above, stellate in outline; tbey are multifid
terminally). (3) Acerate, smooth, slightly and gradually curved,
tapering to sbarp points from c en tre ; size -06 by -0032 millim.
(scattered abundantly tbrougbout sarcode). (4) Stellate, witb about
10-12 straight rays -003 millim. thick at base, tapering to sharp
poiuts, springing from a slight central body '01 to ‘013 millim. in
diameter; expanse of spicule about '05 millim. (5) Stellate like
tbe preceding, but arms about 16 in number and expanse about
•02 millim.
Hab. Providence Reef, Mascarene group, 24 fms.; bottom, sand
and dead coral.
A single specimen witb a somewhat spreading base, wbicb encloses
calcareous fragments, rising into a subcylindrical, terminally rounded,
finger-like column, 30 millim. high and 12 millim. in mean
diameter, slightly overgrown by a delicate Sertularian Hydroid;
extreme diameter of base 40 millim.
The species is most closely allied to Stelletta euastrum, Schmidt,
from Algiers, and to forms so named by Carter (Ann. & Mag. N. H.
1880, V . pp. 135, 136) from Ceylon and Australia, wbicb perhaps
represent another species. Instead of tbe trifid zone-spicule witb
bifurcate arms found in Schmidt’s species, it has simply a subcylindrical
spicule, usually blunt at botb ends, and wants the long
slender acerate; the few-armed stellate has its arms more numerous
(10-12 instead of 2-4, which is tbe range represented by Schmidt’s
'* From the cylmdrical zone-spicule.
S P O N O I I D A . 627
preparation, although ho says tb a t tho range is g re a t); and I do not
find in Schmidt’s species tbo small multiradiate stellate which occurs
b oro; the granulations on tho surface of the disk aro much coarser
in thi,s species. In having lost tho trifid hoad of the zone-spicule it
exhibits tho same tendency as th a t which scorns to bave led in
Ancorina aaptus, Schmidt, to tho loss of all totraradiato characters.
Early stages of tho acerate spicule (no, 3) exhibit tho central inflation
found in tho young acerates of somo lienieree and Spongillida;,
51. Stelletta acerinis.
Ecionemia acervus, Bowerhank, P. Z. S. 1873, p. 322.
There appears to be only one form of minute stcUate; those
stellates in which tbo arms are small, relatively to tbe body, seem to be
tho young form of the longer-armed a d u lt; tbe arms are very .slightly
capitate, as shown by Dr. Bowcrbank’s preparations and still more
plainly in the present specimen, and vary in number from about 5
to about 12. The small acerates are scantily present in tho cortex.
Dr. Bowerbank considered bis specimen to bave been originally
fixed, but the actual base was ab sen t; the present specimen is
decidedly free, and has an oval shape.
Hab. Etoile Island, Amirante group, 13 fms.
Distrihution. Eiji Islands (Bowerhanlc).
52. Stelletta purpurea, var. parvistella, nov.
See P a rt I., p. 473, of tbis Eeport.
A small oval specimen 7g millim. long, destitute of a vent, and of
a purple colour, undoubtedly represents tbis species in a somewhat
modified form. Tbus the stellates do not exceed -0095 mUlim. across
tbe arms, and usually measure about -007 millim., and tbe arms are
generally more numerous than in tbe Australian specimens. Tbe
skeleton-spicules are also somewhat smaller, viz. :—diameter of sbaft
of zone-spicule '032 millim., of anchor about ^023 millim., of acerate
about -025 millim. ; tbe arm of tbe zone-spicule curves boldly backwards,
but does not make an angle in its course like tb at of var.
retroflexa, mibi. Tbe small size of tbe skeleton-spicules is perhaps
partly due to tbe youth of the specimen. Tbe variety approaches tbo
form obtained in tbe Arafura Sea the most closely.
Hah. Providence Reef, Mascarene group, 24 fms.
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