INTRODUCTION. 
The marine fauna of Torres Strait is of more than usual interest because the 
region is generally believed to be one of relatively recent subsidence, and the ques- 
tion naturally arises whether the strait so formed has been a migration route of 
importance in the distribution of marine life. Have East Indian species passed 
eastward through the Strait to give rise to or mingle with the Australian east- 
coast fauna? Or have Australian species passed westward through the Strait 
and entered the East Indian fauna? Correct answers to these questions would 
throw a great deal of light on the origin of the faune of the Australian east coast 
and of the islands in the western Pacific south of the equator. Indirectly, at least, 
light would also be thrown on the whole geological history of those regions. 
Hedley, in his interesting and important paper on the Marine Fauna of Queens- 
land (1909), has touched on these matters and has hinted at some of the evidence 
shown by the distribution of mollusks, but otherwise the questions have hardly 
been approached from a zoélogical point of view. The intensive study of the 
littoral echinoderms of Torres Strait, which was made possible by the expedition 
of the Carnegie Institution of Washington in 1913, suggests that such studies may 
result in finding the true answers to these and similar queries. At any rate the 
results here set forth throw some light on the obscure problems involved. 
Littoral echinoderms are at present one of the best groups of marine organisms 
for the study of such questions because their conspicuousness invites the attention 
of all collectors and has led to the larger common species being well known for many 
years and hence recorded from many places. Moreover, each class of echinoderms 
is sharply defined and none contains such a large number of species as to make a 
reasonable familiarity with all an impossibility for a specialist. Finally, no echino- 
derms are so active or such wanderers in the adult condition, even when they are 
free-swimming forms, as to lead to a rapidly widening dispersion. It is true that 
a large proportion of the known species of echinoderms are believed to have pelagic 
larvee of more or less activity and the dispersal of the species almost certainly 
takes place chiefly by means of the scattering of those larvee by currents, surface 
or deeper. Nevertheless, many species have a relatively restricted range and the 
group as a whole contains comparatively few cosmopolitan or even tropicopolitan 
species. It is also important to note that strictly littoral echinoderms have a 
limited bathymetrical range and species which can be collected on the reefs and 
along shore rarely extend into water over 30 fathoms deep. To such species, there- 
fore, a channel or larger area of greater depth than that forms a barrier which, 
while far from insurmountable, is nevertheless of real importance.! 
Obviously, to make use of a littoral fauna as an agency for throwing light on 
such a problem as the function of Torres Strait in the distribution of marine life, 
the composition of that fauna must be worked out as completely as possible, and 
the first part of this memoir is therefore occupied with an account of the species of 
echinoderms which are known to occur in the Torres Strait region. It is no doubt 
true that this fauna is as yet imperfectly known, for our knowledge is based on 
1 The views here expressed are, I am aware, directly contrary to those held and expressed by Bell (1909), who 
considers that the Indo-Pacific echinoderms can ‘throw no light” on the relation of islands to each other. 
3 
