116 THE ECHINODERMS OF TORRES STRAIT. 
large adults, one with the disk 9 mm. and the other 11 mm. across. The arms are in no 
case perfect, but seem to be 8 to 10 times the disk diameter. The field-notes on the three 
specimens are as follows: 
“Radial shields small, bare. Yellow stripe on arm, interrupted every few plates by red trans- 
verse band (i.e., every fourth or fifth plate is red). General color greenish-yellow, not bright; most 
under arm-plates have a small dusky spot at center. 
“Radial shields bare; rest of disk thickly covered with rather stout spines; arms rather long, 
with a broad yellow stripe above and also below. 
“Disk red-brown; arms about 8 to 9 X disk, dull olive regularly banded with darker; under a 
lens the radial shields are seen to be bordered with white, with a black border inside it; the yellow 
stripes on each surface of arm very prominent; there are yellow markings also on each side of each 
upper arm-plate.” 
In the dry specimens, the red and yellow shades have entirely disappeared and even 
the olive is only faintly indicated. The general coloration is simply variegated blue and 
white, with a conspicuous longitudinal white stripe on the arm. The affinities of virgata 
seem to be with hirsuta, punctolimbata, etc., but its specific characters appear to be constant. 
The specimens taken at Mer were found underneath rock fragments on the reef-flat at 
widely separated points. 
Ophiomaza cacaotica. 
Lyman. 1871. Illus. Cat. M. C. Z., No. 6, p. 9, pl. i, fig. 15.—Déderlein. 1896. Jena. Denkschr., 8, pl. xvii, 
figs. 26, 26a. 
(Plate 16, Figure 3.) 
This very interesting brittle-star was not common at Mer, only two typical specimens 
being taken. One of these was almost black, but was commensal with a bright-red Coma- 
tula purpurea, while the other corresponded very closely in color to the nearly black Coman- 
thus annulatum on which it was found. A small specimen of the variety picta, character- 
ized by the presence of white in the color pattern (pl. 16, fig. 3), was found on a dark 
specimen of annulatum. After watching these few specimens and those of O. obscura, as 
we saw them on the comatulids and in the laboratory, I have no doubt whatever that 
Ophiomaza is normally commensal with comatulids, is particularly adapted to the life, 
and does not occur apart from comatulids, except as the result of accident or possibly 
while passing from one to another. I doubt whether such passing occurs, however, so 
long as the protecting crinoid is living and healthy. 
The distribution of cacaotica is very wide, as it is known from Zanzibar and the Gulf 
of Suez to New Caledonia. Bell records it (1884) from Port Molle, Queensland, and (1894) 
from northwestern Australia, 8 to 20 fathoms. It has been taken in Torres Strait by each 
of the four collecting parties that have been there. But excepting our observations at Mer, 
nothing seems to have been reported as to the comatulids with which it has been found. 
Ophiomaza cataphracta. 
Liitkenia cataphracta Brock. 1888. Zeits. f. w. Zool., 47, p. 522.—Koehler. 1904. Mém. Soo. Zool. France, 
17, p. 114, figs. 92, 93. 
Ophiomaza cataphracta H. L. Clark. 1915. Mem. M. C. Z., 25, p. 283. 
The unique holotype of this interesting species is said to have been from Cape York, 
Australia. 
Ophiomaza obscura. 
Ophiocnemis obscura Ljungman. 1867. Ofv. Kongl. Vet.-Akad. Férh., 23, p. 333. 
Ophiomaza obscura Lyman. 1874. Bull. M. C. Z., 3, p. 233. 
(Plate 16, Figure 2.) 
Three individuals of this handsome species were found on specimens of Comanthus 
annulatum, and the largest and most finely colored was chosen to illustrate the species 
(pl. 16, fig. 2). The other specimens were darker and duller and there were no markings. 
