114 THE ECHINODERMS OF TORRES STRAIT. 
identification could be ‘‘without doubt” in the face of this remarkable discrepancy, espe- 
cially as the arm-spines were also noticeably different. On the whole I think rotata must 
be considered a dubious species and its occurrence in Torres Strait very uncertain. 
Ophiothrix stelligera. 
Lyman. 1874. Bull. M. C. Z., 3, p. 237; pl. iii, figs. 15-20. 
(Plate 16, Figure 8.) 
This species ranges from Zanzibar to Fiji, and according to Koehler (1907) it extends 
as far south on the western coast of Australia as Koombana Bay. It is common at the Aru 
Islands. As even adults rarely exceed 8 mm. in disk diameter and the growth-changes are 
not yet worked out, it is probable that some records are erroneous. The species characters 
are not well-marked or very constant and confusion with other species has unquestionably 
occurred. Both the Challenger and Dr. Semon took specimens in Torres Strait, referred 
to stelligera by Lyman and Déderlein respectively. At Mer a number of examples of an 
Ophiothrix were taken which agree well with each other and fairly well with the type of 
stelligera, except in color. Rather more than half of these were found on sponges brought 
up by the Japanese diver from 18 fathoms off the northwestern reef, October 13, 1913. 
These specimens were of a pinkish color with a median white stripe on the dorsal side of 
each arm; a few were pale purple instead of pink. All of the other examples referred to 
stelligera were found among the coral fragments on the southwestern reef. In them the 
disk was reddish or yellowish (pl. 16, fig. 8) or dull greenish, and the arms were pale purple 
with slightly reddish spines, or dull purplish or greenish. In the dry specimens, red and 
pink tints are entirely lost, and pale brownish or dull purplish, light or dark, are the 
prevailing shades. 
Ophiothnix striolata. 
Grube. 1868. Jahrsb. Schles. Ges. Vaterl. Cult., 45, p. 45.—Déderlein. 1896. Jena. Denkschr., 8, pl. xvii, 
figs. 22, 22a. 
(Plate 15, Figure 1.) 
This handsome species is well known from the East Indies, and was taken in Torres 
Strait by both the Alert and Dr. Semon. Déderlein says the latter brought many specimens 
from Thursday Island. Koehler (1907a) lists striolata from as far south on the West 
Australian coast as Fremantle. We did not find the species at Mer, but one small specimen 
was taken from under a stone on the sand-flat southwest of Friday Island, September 13, 
1913. ‘This individual was so prettily colored with green and brown that Mr. Grosse 
made a drawing of it (pl. 15, fig. 1). On being treated with formalin and corrosive subli- 
mate and then dried, the colors underwent a remarkable change, the brown becoming 
purple and the green yellow. With the lapse of time these shades have altered still further 
and the specimen is now whitish and deep blue, as are all the other specimens of striolata 
in the Museum of Comparative Zoélogy. So far as I know, this striking difference between 
the colors in life and after preservation has not previously been noted; it is more marked 
in striolata than in any other Ophiothrix with which I am acquainted. 
Another very notable and puzzling feature of this species is the presence in young 
specimens of a membrane on the arm-spines on the basal part of the arm, as in Ophiopteron. 
The degree to which this membrane is developed differs in different individuals; it is often 
very thin and easily ruptured, but it may be as thick and as complete as could be asked. 
I think Ophiopteron puncto-ceruleum Koehler, of which a cotype is in the Museum, is 
based on the young of Ophiothrix striolata, but there is not sufficient material at hand to 
permit a final decision. If such should be the case, the status of Ophiopteron and its rela- 
tion to Ophiothrix would require a careful investigation. As usual in such cases, abundant 
material of all ages is urgently needed. 
