212 CRITIQUES AND ADDRESSES. [ix. 



at the close of the Mesozoic period. An Australian 

 fauna would be found underlying an American fauna, 

 and the transition from the one to the other would be as 

 abrupt as that between the Chalk and lower Tertiaries ; 

 and as the drainage-area of the newly formed extension 

 of the American continent gave rise to rivers and lakes, 

 the mammals mired in their mud would differ from those 

 of like deposits on the Australian side, just as the Eocene 

 mammals differ from those of the Purbecks. 



How do similar reasonings apply to the other great 

 change of life that which took place at the end of the 

 Palaeozoic period ? 



In the Triassic epoch, the distribution of the dry land 

 and of terrestrial vertebrate life appears to have been, 

 generally, similar to that which existed in the Mesozoic 

 epoch ; so that the Triassic continents and their faunae 

 seem to be related to the Mesozoic lands and their faunae, 

 just as those of the Miocene epoch are related to those of 

 the present day. In fact, as I have recently endeavoured 

 to prove to the Society, there was an Arctogaeal continent 

 and an Arctogaeal province* of distribution in Triassic 

 times as there is now ; and the 'Sauropsida and Marsu- 

 pialia which constituted that fauna were, I doubt not, 

 the progenitors of the Sauropsida and Marsupialia of 

 the whole Mesozoic epoch. 



Looking at the present terrestrial fauna of Australia, 

 it appears to me to be very probable that it is essentially 

 a remnant of the fauna of the Triassic, or even of an 

 earlier, age ; ' in which case Australia must at that 

 time have been in continuity with the Arctogaeal 

 continent. 



But now comes the further inquiry, "Where was the 



1 Since this Address was read, Mr. Krefft has sent us news of the discovery 

 in Australia of a freshwater fish of strangely Palseozoic aspect, and apparently 

 a Ganoid intermediate between Dipterus and Lepidosiren. 



