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148 COLLECTIONS FROM MELANESIA.
a lm o st black), th e differences in th e e x te n t to w h ich th e papillte are
developed, an d th e comparatively much g re a te r firmness of th e
in te g um e n t of th e yo u n g er specimens help ns to u n d e rs ta n d how it
is th a t several different names have been given to th is Avidely distrib
u te d species. On th e o th e r h an d , i t is well to s till b e ar in mind
th a t our kuoAidcdge of H o lo th u ria n o rg an iz a tio n is n o t y e t so comp
le te as to ju s tify us in definitely a sse rtin g th a t fresh d iffe rential
m a rk s do n o t y e t rem a in to he d iscovered; if th e re a re such, th e
series now reg a rd ed as single may be sh ow n to co n ta in rep re sen ta
tiv e s of more th a n one form.
As th e only illu s tra tio n of th e spicules appears to he th a t w h ich
has been given by Prof. Semper, I have h a d vicAvs made of th em
from th e side to show th e ch a ra c te rs of th e free p ro je ctin g processes,
an d from below shoAving th e inside of th e hemisphere.
Port Molle; Port Denison ; Torres S tra its; xilert Island (Torres
Straits), 17 fms., sand.
G. Colochirus australis.
Ludicig, Seinper’s Arbetten, ii. p. 88.
This species, which is represented by only one specimen from Port
Molle (14 fms.), was more richly so in a collection forwarded some
three years ago from Port Jackson by Mr. J. Brazier. I do not,
however, find th at the suckers are in them brown in colour, while
the tentacles ai’e rather black and w'hite than brown and yellow.
Neither of these are, however, points of any real importance. I
find, from Mr. Eamsay’s collections, th at this species is very abundant
in Port Jackson.
7. Actinocucumis difficilis. ( P l a t e IX. fig. C.)
I have had the greatest difficulty in assuring myself of the specific
distinctness of this form from the A . typica of Ludwig, the variations
exhibited in the present collection impressing one with the
necessity of the greatest care in the delimitation of species.
The species may perhaps he most conveniently described by
pointing out the several characters by which it is to be distinguished
from A. typica. The amhulacral papilla? on the dorsal surface are
rare, and the sirckers are not in more than four rows for each ray ;
the differences in the form of the spicules will he best seen by comparing
the figures now given with those drawn by Professor Ludwig.
The retractors are inserted rather further back, being found at 24
miUim. from the anterior end in a specimen 65 millim. long, and
a t 22 millim. in one 70 millim. long; the genital tubes are shorter
than in A . typica, being not more than 15 millim. long in any specimen
examined. The Pollan vesicle would also appear to be shorter,
being only 7'5 millim. long in a specimen of 65 millim. length. I t
may be added th a t the loop of the intestine is exceedingly s h o rt;
th at the tentacles, which are not always 20, sometimes seem to
ECHINODERMATA. 149
belong to an outer, and at others to an inner circle on the d isk ; and
th at the colour which in some cases is light brown, in others is
purplish grey.
Albany Islan d ; Torres Straits.
Quite recently an example of this species has been received from
Kurrachee.
8. Thyone mirahilis (?).
Thyone mirabilis, Ludioig, Seinper's Arbeiten, ii. p. 93.
The form of the spicules would perhaps allow us to place the
single specimen here with doubt referred to this species either ivith
it or with Holothuria dietrichii of Ludwig, the supporting-rods in
the suckers of the latter not being figured. Though our specimen
has much more the form and colour, so far as one may judge from
the description, of the Holothurian, the eight large arborescent and
two small tentacles, the scattered sucker-feet, and the unarmed
anal orific exactly determine its generic affinities.
Port Denison.
9. Thyone sacellus *.
Stolus sacellus, Selenka, Zeit. f. wiss. Zool. xvii. p. 355.
Thyone rigida, Semper, Holothurien, p. 66.
Thyone sacella, von Marenzeller, Verh. z.-bot. Ges. Wien, 1881, p. 134.
Torres Straits.
10. Thyone okeni. (P late IX. fig. D.)
The two specimens of this species are in remarkably good condition
for examination, as one died with its tentacles fully expanded
and the other was laid open by the collector.
With the exception of the terminal plate in the suckers I have
not been able to detect any calcareous bodies either in the suckers
or the integument; and if any such are present they must be exceedingly
small and very rare. This characteristic brings this
species into proximity to 1;he T. villosa of Semper, where, as in this,
the suckers are very closely packed.
Elongated in form, very dark brown in colour (in spirit), tentacles
of about the same shade ; suckers closely packed and distributed over
the whole body, their radial arrangement in the region of the anus
very obscurely indicated. Anus without teeth. Eetractors inserted
very nearly as far back as the middle of the body. Calcareous ring
of ten pieces, the radial similar to the interradial, elongated, and
wider below than above (fig. D). Calcareous plating extends some
way along the enteric tract (fig. D). Genital tubes numerous, very
slender and long, inserted behind the middle point of the length of
* Prof. Selenka has been kind enough to inform me that sacellus, as used
by him, is a diminutive form of saccus, not of sacer.
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