COMPOSITION AND ORIGIN. 207 
The characteristically Australian fauna of list 4 does not afford any evidence 
in support of a Pacific influx. Apparently it has come in along either side, or, 
perhaps better, along both sides of the Arafura Sea. Among the 20 comatulids, 
only a single species is known from either Fiji or Samoa, and only 1 or perhaps 2 
others occur on the shores of eastern New Guinea or the islands to the east and 
southeast; but 9 of the species are East Indian, and all of the others find their 
nearest relatives in that region. The sea-stars tell the same story, only one of the 
11 occurring at Fiji or Samoa, 6 being found in the East Indies, and all the others 
having their nearest relatives there. So, too, of the 13 brittle-stars only 2 occur at 
Fiji or Samoa, 8 or 9 occur through the East Indies, and the remaining 2 or 3 are 
certainly very nearly related to East Indian forms. There are only 8 echini to be 
considered; of these only Tripneustes is found at Fiji or Samoa, and only 1 or 2 
are as yet known to be East Indian species, but the affinities of the others are so 
unmistakably East Indian as to admit of no discussion. Of the dozen holothurians, 
4 occur at Fiji or Samoa, but these and all the others, except Actinocucumis typicus, 
are East Indian species. Thus, out of 64 characteristically Australian species, 
only 9 are found at Fiji, but about 36 occur more or less generally in the East 
Indies and all the remainder have unmistakable East Indian relationships. It is 
of particular interest and perhaps importance to note that apparently about one- 
third of this group are more or less peculiar to Australia or to Australia and the 
Aru Islands, and while their nearest relatives are East Indian, they have become 
specifically distinct from those forms. 
The 34 species of list 6 are as distinctly East Indian as those of list 4, for while 
7 are known from either Fiji or Samoa, 30 species are characteristically East Indian 
and the other 4 find their nearest relatives there. The distribution of some of the 
species in this list is peculiar, notably that of Arachnoides placenta, which occurs 
in New Zealand as well as along the Malay Peninsula. It is one of the very few 
echinoderms of the Torres Strait region which occur in New Zealand waters. Its 
distribution is best explained as follows: Originating in the East Indian region, it 
extended southward to the Moluccas and southeastward to Fiji and finally to New 
Zealand; later, with the opening of Torres Strait, it has extended down the eastern 
coast of tropical Queensland; it may have reached New Zealand via the New 
Caledonian ridge, but as it is not yet recorded from New Caledonia, it seems more 
likely that it arrived via Fiji. 
THE USE OF TORRES STRAIT AS A MIGRATION ROUTE. 
Turning now to Hedley’s third hypothesis, that the breaking through of Torres 
Strait led to a movement westward and northward of a Queensland coastal fauna, 
we are confronted at once with the difficulty of securing evidence, since there is no 
characteristic Queensland echinoderm fauna, save what has apparently been derived 
from the Pacific. Nevertheless, it is conceivable that after the opening of Torres 
Strait the Pacific influx of echinoderms moved westward as well as southward. 
If it moved northwestward to the Moluccas and rejoined the Indo-Pacific fauna, 
the circuit of New Guinea would be complete and all evidence as to the westward 
