356 AUSTRALIAN, SOUTH AFRICAN, AND INDIAN COAL-MEASURES. 



But in the middle of this period (taken as a whole) the 

 pendulum swung back, and an intervening period of depression 

 and refrigeration took place. Vast rivers, swift in their upper 

 courses, and carrying with them into their lower waters enor- 

 mous volumes of sand, which they, with their diminished fall, 

 were unable any longer to carry through into the ocean, accumu- 

 lated about their shifting beds the enormous masses of the 

 Hawkesbury sandstone and its southern equivalents. 



In this rock we have evidence, not as yet found in the Lower 

 Clarence beds, of the introduction of many Ganoid fishes, of 

 Labyrinth odonts, a,nd of the existence of other forms whose pre- 

 sence seems at present inexplicable. Upon the hypothesis here 

 adopted it would seem probable that the fish and amphibia had 

 really made their way into this region during the preceding period 

 of emergence (period of the Lower Clarence beds), and during 

 the existence of a temporary " bridge " between Australia and 

 S. E. Asia. In the same way one would account for the con- 

 temporary introduction of Labyrinthodonts in the New Zealand 

 regions. And I have more than once shown that it is at least 

 not improbable that Ceratodus and Osteoglossum (besides 

 Hatteria) managed to effect their entrance at the same time. 

 After the Hawkesbury interregnum, the restoration of more 

 equable climates, owing probably to yet another emergence of the 

 land, is testified to by the Coal Measures of the Upper Clarence 

 beds, of Ipswich in Queensland, and of Newtown and Jerusalem 

 in Tasmania. 



If the formations of this period do really graduate upwards 

 into the Marine Cretaceous beds of the Kolling Downs series, as 

 suggested by Mr. Jack (above, p. 340), we have here before us a 

 complete record of the very uneventful history of this ancient 

 flora of Australia, from the Lower Carboniferous of both hemis- 

 pheres to the Upper Jurassic of the southern, far poorer and more 

 antique and, as it were, obsolete, than the contemporary flora of 

 the north. 



The breaks in the record are but two — one between the Lepido- 

 dendron and the Glossopteris flora, the other between the latter 

 and the Tseniopteris. 



(To be continued.) 



