COMPOSITION AND ORIGIN. 203 
Queensland littoral fauna with a characteristic facies; (2) that the influx of Pacific 
forms from the east reached and came into competition with this early fauna; and 
(3) that the opening of Torres Strait led to a movement of this Queensland fauna 
northward and westward to the Moluccas and West Australia. 
THE GULF OF QUEENSLAND HYPOTHESIS. 
As regards the first of these hypotheses, we have already seen (p. 198) that the 
echinoderms offer no evidence in support of it. There is a very distinct Australian 
echinoderm fauna, but it occurs primarily on the southeastern and southern coasts 
of the continent, and the further north one goes on the Queensland coast the less 
it is to be found. Apparently none of it reaches the Torres Strait region, nor is 
there any reason to believe it ever extended any further north than it does to-day. 
If, therefore, a Jurassic Gulf of Queensland existed, it is evident that it had a very 
scanty echinoderm fauna, if any. Even the great gulf (now the Coral Sea) postu- 
lated by Hedley as existing at the close of the Mesozoic seems to have lacked echino- 
derms. If this conclusion is erroneous, they were apparently overwhelmed by the 
influx from the Pacific, when the ridge of which the Solomons are the remains was 
finally broken through, for that the hypothesis of this influx is supported by the 
present study of Torres Strait echinoderms admits of little doubt. 
THE PACIFIC INFLUX HYPOTHESIS. 
Of course the influx of Pacific echinoderms was not a sudden inrush following 
a catastrophic alteration of the Solomons ridge. On the contrary, it was evidently 
a slow introduction of species abundant in the East Indies and western Pacific, 
which gradually extended their range southwestward into the slowly deepening 
bays and channels which have finally separated the islands of the Solomon and 
Bismarck Archipelagoes. We have as yet no clue as to just where the first con- 
nection between the Pacific and the Coral Sea of to-day was located, but there seems 
little doubt that it was between the Solomons and the New Hebrides. Along its 
northwestern coast the ancestors of the present echinoderm fauna of the Queensland 
coast pushed their way. Among these early immigrants were comatulids of the 
genera Comatella and Comatula, sea-stars of the genera Astropecten and Asterina, 
brittle-stars of the genera Ophiactis, Ophiothrix, and Pectinura, sea-urchins of the 
genera Phyllacanthus, Tripneustes, Brissus, and Maretia, and holothurians of the 
genera Leptosynapta and Thyone. All these genera have reached New South Wales 
and all are characteristic of the western Pacific. In some cases endemic species 
have developed on the Australian coast, but in others the forms from even as far 
south as New South Wales are not yet to be distinguished from those of the Pacific. 
The great group of echinoderms given above in list 5 and designated “the 
Barrier Reef group,” are the present representatives of the element in the Queens- 
land fauna originating with the Pacific influx. A detailed study of that group is 
fully warranted by some of the really important facts which it reveals. 
The 10 comatulids represent 5 genera, all of which range from the western 
Indian Ocean to the western Pacific, with their center in the East Indian region. 
All except Comanthus alternans are known from New Britain, New Caledonia, or 
