108 THE ECHINODERMS OF TORRES STRAIT. 
able, therefore, that it is commensal, but although we examined scores of the comatulid, 
no other examples of the brittle-star were seen. Its nearest allies in the genus seem to be 
O. nama from Fiji and the Kermadecs, and O. pteropoma from Japan, but both these species 
are known only from rather deep water (191 to 610 fathoms). 
There is an unfortunate error with reference to the habitat in my original account of 
this species. By a slip of the pen, the depth “18 fms.” is inserted, whereas the comatulid 
on which this specimen of Ophiactis occurred was found far out on the southwestern reef- 
flat near extreme low-water mark, on October 27, the last day of collecting at Mer. Our 
only collecting at 18 fathoms was done two weeks earlier by a Japanese diver, when the 
holotype of O. luteomaculata was found. 
Ophiactis hemiteles. 
H. L. Clark. 1915. Mem. M. C. Z., 25, p. 262, pl. 10, figs. 7, 8. 
(Plate 16, Figure 1.) 
When this handsome brittle-star was extricated from a fragment of coral rock on the 
southwestern reef at Mer, October 2, 1913, it was supposed to be an Amphiura, and the 
correct genus was not determined until the specimen was in Cambridge. The long, taper- 
ing arms with their numerous, slender arm-spines are most unlike typical Ophiactis, but 
the single large tentacle-scale and the mouth armature are very characteristic. Unfortu- 
nately, the specimen autotomously ruptured its arms while the colored drawing was being 
made and the preserved specimen retains little of its original beauty. The species is an 
isolated one, not nearly related to any other member of the genus. 
Ophiactis luteomaculata. 
H. L. Clark. 1915. Mem. M. C. Z., 25, p. 263, pl. 11, figs. 7, 8. 
(Plate 13, Figure 6.) 
Although the holotype was found in a sponge, in 18 fathoms of water, off the north- 
western reef at Mer, we found no other specimens anywhere in Torres Strait. But the 
Endeavour, 11 miles southeast of Ballina, New South Wales, in 27 to 29 fathoms, collected 
a fine series of sea-urchins (Prionocidaris australis), among the spines of which this odd 
little brittle-star seemed to be quite common. The smallest specimens had 6 arms and 
were clearly reproducing by fission, but the adults were symmetrically pentamerous 
like the type. The orange-colored radial shields are a good distinguishing mark for living 
specimens, but unfortunately the color is fugitive and is wanting in preserved material; 
but a dark spot or band at the middle of the larger arm-spines seems to be a persistent 
characteristic marking. 
Ophiactis modesta. 
Brock. 1888. Zeits. f. w. Zool., 47, p. 482.—Déderlein. 1896. Jena. Denkschr., 8, pl. xv, figs. 5-5b. 
This species was originally described from Amboina, but Semon took two specimens 
of Ophiactis near Thursday Island which Déderlein refers to it. We did not meet with it. 
Ophiactis savignyi. 
Ophiolepis savignyi Miller and Troschel. 1842. Syst. Ast., p. 95. 
Ophiactis savignyi Ljungman. 1867. Ofv. Kongl. Vet.-Akad. Forh., 23, p. 323.—Liitken. 1859. Add. ad 
Hist. Oph., pt. 2, pl. iii, figs. 7a, 7b. 
This tropicopolitan species is common in Torres Strait, especially in red and yellow 
sponges. It is less common where sponges are infrequent, but at Mer it was sometimes 
common in the dead organ-pipe coral (T'ubipora). 
