104 THE ECHINODERMS OF TORRES STRAIT. 
OPHIUROIDEA. BRITTLE-STARS. 
The ophiuran fauna of Torres Strait is exceedingly rich, but so many of the 
species hide themselves in the crannies of corals and of coral rock, they are easily 
overlooked, and general collectors are apt to pass them by. Thus the Challenger 
naturalists gathered only half a dozen species, and such zealous collectors as 
Coppinger and Semon did not uncover more than a small fraction of this very 
interesting fauna. The Alert collection contained 9 species, only 1 of which was 
taken by the Challenger, while Semon gathered 14 species, 3 of which were found 
by the Challenger and 5 others by the Alert. The only brittle-star common to all 
three collections is the symbiotic Ophiomaza cacaotica, which we also found on sev- 
eral occasions at Mer. Of the other 19 species known from the region in 1913 we 
found only 8, but we discovered 14 species new to science at the time! and 37 others 
not previously recorded from Torres Strait. 
There are, then, no fewer than 71 brittle-stars now known from this restricted 
area, but I have no doubt many additional species will be found by the next col- 
lector interested in the group. Most of the species are found associated with coral, 
or under fragments on the reef-flat. Little effort has yet been made to collect mud- 
loving species or those living on ‘‘weedy”’ bottoms, and very few of these forms are 
as yet known. Of the 71 species, 18 or a full quarter belong to the tropicopolitan 
genus Ophiothriz, the most perplexing group in the whole class. About a third of 
the 18 species are ill-defined and of more or less doubtful status, and the material 
at hand, even taken in connection with experience on the Torres Strait reefs, does 
not enable me to undertake an adequate revision of the genus. The family Ophio- 
comide is represented in the Torres Strait region by 16 species, and in this case 
sufficient material is at hand to enable me to give a complete revision of the family. 
But such a revision is much less difficult and much less useful than a revision of 
Ophiothrix would be. 
Unlike the sea-stars, brittle-stars are commonly more or less gregarious, and 
where one specimen occurs others are almost sure to be found. Of the 59 species 
we collected, about half were common or abundant, and half a dozen of these 
swarmed wherever conditions were suitable. In most cases, however, a given 
species occurs only in a particular habitat, and those which occur near the shore- 
ward side of the reef-flat are wanting near the outer edge of the reef. Very few 
brittle-stars occurred among living corals, but the dead portions of clusters of 
Seriatopora swarmed with individuals of many common species. Every coral 
fragment or piece of rock large enough not to be moved about by ordinary tides is 
a shelter for brittle-stars, and if the shelter is large and has been undisturbed for 
some time, many species will be found together there. Of the brittle-stars which 
were found but once, it is safe to say all are small, inconspicuous species, living in 
the crannies of dead corals and rock fragments, and the failure to secure more 
specimens is as a rule due rather to their secretiveness than to their actual rarity. 
*See H. L. Clark, 1915. Catalogue of Recent Ophiurans. Mem. M. C. Z., 25, p. 165-376, pls. 1-20. 
