110 THE ECHINODERMS OF TORRES STRAIT. 
a type. Specimens of Ophiothriz regarded as hirsuta have been recorded from Zanzibar 
and the Red Sea on the west to the Riu Kiu Islands and northwestern Australia on the 
east and south. At Mer, one long-armed Ophiothrix was taken, which I identified and 
have recorded (1915, Mem. M. C. Z., 25, p. 272) as this species. 
Ophiothrix liodisca. 
H. L. Clark. 1915. Mem. M. C. Z., 265, p. 273, pl. 12, fig. 3. 
The holotype of this well-marked species was found on the underside of a coral frag- 
ment far out on the southwestern reef at Mer, on the last day of our stay, October 27, 1913. 
The remarkably flat and smooth disk is a striking feature and the coloration is also notable. 
The pattern is well shown in the dry specimen and is more conspicuous than it was in life; 
the ground-color is pale olive, the distal tips of the radial shields with white markings; 
upper surface of arm with a narrow, median, pale-brownish stripe, bordered on each side 
with a broader white stripe which is bounded on the outer side with a narrow dark-olive 
line. The striped arms were not noted as such in the fresh specimen, my field-notes saying 
only: ‘Coloration very delicate; orange markings on upper surface of arms when seen 
through a lens.”’ 
Ophiothrix longipeda. 
Ophiura longipeda Lamarck. 1816. Anim. 8. Vert., 2, p. 544. 
Ophiothriz longipeda Miiller and Troschel. 1842. Syst. Ast., p. 113. 
(Plate 15, Figure 5; Plate 33, Figure 1.) 
It is odd that this, one of the longest-known, commonest, and most conspicuous 
members of the genus, has never been figured hitherto. I have therefore thought it well 
to show the general appearance of a dry specimen, as photographed (pl. 33, fig. 1). The 
colored figure given by Herklots (1869, Echinod. peintes d’aprés nature, pl. 7) is so unlike 
any specimen of longipeda I have seen, either living or preserved, that the identification of 
his original seems to me dubious. 
I first saw longipeda alive August 5, 1913, on the reef at Papeete, Tahiti, where it is 
very common; my field-notes say the colors in life were pale olive-green and brownish, 
and that they changed in alcohol. At Green Island, near Cairns, Queensland, large speci- 
mens similar to those at Tahiti were common, September 6, 1913. At every place where 
we collected in Torres Strait longipeda was common, living under or in the fragments of 
coral rock. It is extraordinary into how small a cavity the long arms can be crowded. In 
the largest specimen noted, the disk was 37 mm. across in life, and the arms were about 
625 mm. long, but not many individuals are so large, the average size for an adult being 
20 to 30 mm. across the disk with arms 400 to 500 mm. in length. The coloration of the 
Torres Strait specimens was fairly constant, variegated yellowish and purplish, with dark 
under arm-plates and upper arm-plates speckled with bluish-purple. The blue and purple 
shades are apt to be emphasized by alcohol, but some individuals are very distinctly 
purplish-blue in life. In typical specimens the arms do not show any longitudinal stripes. 
The amount of yellow varies a good deal in different individuals and is sometimes so great 
as to be very striking; one such specimen was found near the close of our stay at Mer 
and was drawn by Mr. Grosse (pl. 15, fig. 5). 
It is very desirable that the growth-changes of this species should be worked out, but 
the material collected at Mer in September and October 1913 is not adequate for the pur- 
pose. The extent of individual and of geographical variation in arm-length and color 
also needs much more extensive study than has yet been possible. When this has been 
satisfactorily done, I believe longipeda will be regarded as the type of a genus, distinct 
from Ophiothrix proper, and containing several species. Meanwhile, the specific limits of 
longipeda itself are not at all definite. It seems to be a protean form of very extended 
