i
become less conspiciious aud much reduced; the white lines along
the arm are broken into by blue patches, much less extensively developed
than in the dark fo rm; on the loiver surface of the arm
the blue lines may bo present as continuous tracts, or they may here
and there be interrupted by white.
Port Curtis ; Thursday Island ; Port Darwin.
16. Ophiothrix striolata.
Lyman, p. 36.
Thursday Island.
17. Ophiothrix galateae.
Lyman, p. 36.
Port Darwin.
18. Ophiothrix ciliaris.
Lyman, p. So.
Port Jackson, 0 -5 fm s .; Port Molle.
19. Ophiothrix rotata.
Martens, Arch.f. Nat. 1870, p. 258.
A single specimen, without doubt referred to this species, differs
in one or two points from th at described by Dr. von Martens. In
the Perlin-Museum specimen the diameter of the disk is 7 millim.,
and the length of the arms 35 millim. In our specimen the arms
must have been nearly 150 millim. long, while the diameter of the
disk is 12 millim. Tho upper spines are not more than twice the
Avidth of the arm, instead of four times. The original descriher
makes tivo statements with regard to the colour of the oral shields :
—“ Unterseite der Scheibe mit den Mundschildern und die Armstacheln
blass ” ; and “ Das der Madreporenplatte zugehörige Mundschild
ist merklich grösser, an den Seiten nicht eingebuchtet und
weiss, nicht wie die ändern violett.” Tn the specimen now under
examination there is some violet marking on each one of the mouth-
shields.
Thursday Island, 3 -4 fms.
So far as the present collection allows me to form any ideas with
regard to the range of variation within the limits of a “ species,” and
the value of the colour-markings on which previous investigators have
laid, and, as it seemed, justifiably, very considerable stress, I am in clined
to the view th at the variation is very much greater than was
supposed, and that, after all, colour-marking, though an important
aid in the discrimination of the species, can hardly be said to have
the value which has been attached to it. The doubts first raised
by a study of 0. martensi {vide supra) are not a little strengthened
by the three specimens now lying before me, ivhich, I have little
doubt, will be seen, wheu a large series is to hand, to be nothing
more than varieties of 0. rotata. As none of the arms are complete,
the measurements I could give might only be deceptive ; in them the
upper arm-spines are proportionately larger th an in the specimen
already spoken of; the bands separating the plates, the character of
which has given rise to the specific name, may vary in breadth on one
and the same disk; and the grannies may be in narrow or broad hands,
and may be so greatly elongated th at they may more correctly be
spoken of as spines ; tho marking would by some be spoken of as
exceedingly characteristic, for there extend from the disk on to the
arms two lines of dots of blue ; at every fourth plate, when regular,
the two dots of either side fuse, and the spot enlarges into a blue
patch ; an exactly similar marking is to be seen on the lower surface.
In the specimen unhesitatingly placed with 0. rotata there is
not this definite arrangement of the dots.
I have thought it right to direct attention to these peculiarities,
but a full and satisfactory discussion of the subject must be based
on a much larger series of specimens.
These examples were also from Thursday Island.
20. Ophiothrix piinctolimhata.
Martens, Arch.f. Nat. 1870, p. 257.
Port Curtis ; Port Molle ; Thursday Island, 3 -4 fm s.; Prince of
Wales Channel; AVarrior Reef.
The specimen from Port Curtis, which is smaller than the others,
has the lateral spines proportionately longer, more echinulated, and
much more glossy.
21. Ophiothrix longipeda.
Lyman, p. 35.
Port Curtis ; Port Molle.
22. Ophiothrix microplax.
Disk large, covered with short spines, less thick on the radial
shields ; ends of the not-thorny arm-spines faintly clavate. Proportion
of arms to disk about 6 to 1.
The disk is rather large (20 millim. in diameter) and is covered
with very short spines, which may almost he described as spinous
granules; these are not so closely packed on the radial shields or on
the actinal surface as on the rest of the disk. The radial shields
are small, elongated, triangular, the straight base of the one faces
th a t of the other ; the plates of each pair are separated by several
elongated scales, which carry a few longer spines. There is some
imbrication of the scales on the actinal surface of the disk.
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