260 ME. W. T. BLANFORD ON THE OCCURHENCE OF 



enormous change that took place in all life, vertebrate and inver- 

 tebrate, animals and plants, in the interval between Upper Palaeozoic 

 and Lower Mesozoic times. Despite all the discoveries of Palseozoic 

 types in the Trias, and of Mesozoic genera in Upper Carboniferous 

 or Permian, that have taken place in the last forty years, the fact 

 remains as distinct as it was when it formed the subject of Prof. E. 

 Porbes's Presidential Address to the Society in 1854, that a greater 

 change in forms of life takes place between Permian and Trias than 

 between any other two consecutive systems in the whole of geolo- 

 gical time. If the views above expressed be correct, and if during 

 part of the Carboniferous period an excessively low temperature 

 prevailed, some explanation of the change may be found. The alter- 

 ation in marine life at the close of the Palaeozoic period appears to 

 have been enormously greater than anything produced by the last 

 glacial epoch, the effects of which, indeed, may be said scarcely to 

 have influenced the tropical seas, although in places, as in India, 

 the modification of the land- faun a and flora has in all probability 

 been extensive. The circumstance that the temperature towards 

 the end of the Palaeozoic era must have been lower than in the 

 Pleistocene epoch, may account for the occurrence of boulder-beds of 

 the former date in tropical and subtropical countries. 



Under the impression that the Indian Damudas were of later date 

 than the Newcastle beds of Australia, the idea has been suggested 

 by several writers* that the European Mesozoic flora originated in 

 Australia in Palaeozoic times, was driven to the equator by the 

 increasing cold in the Permian epoch, and thence spread again to 

 the northward in Mesozoic times as the temperature improved. 

 This may be partially the fact, but it is not necessary to invoke the 

 aid of migration to the same extent. It is at least equally probable 

 that a considerable tract of Southern Asiat in Carboniferous times 

 formed part of a continuous land area extending to Australia on 

 one side and to South Africa on the other, that this land area was 

 absolutely severed from all the countries in which the Coal-measure 

 flora existed at the time, and was subjected to a much colder climate. 

 It is unnecessary to remark that the Coal-measure flora was long 

 since proved not to have required a tropical climate for its develop- 

 ment. The distinction between the two floras is in all probability 

 due to long isolation — to a difference, in short, of geographical areas 

 with a distinct biological history, or of what are generally known as 

 botanical regions. 



Discussion. 



The Peesidekt remarked upon the wide range of the paper. In 

 the case of some communications hardly more than two or three 

 Fellows could be expected to take part in the discussion ; but in the 



* Manual G-eol. India, Introduction, p. xxxvi ; Oldham, J. A. S. B. vol. liiL 

 pt. 2, p. 195 ; Waagen, Rec. G. S, I. 1886, p. 37. 



t Gondwana plants, mixed up in an extraordinary manner with each other 

 and with European Rhsetic types, have been found in Tonquin. Zeller, BulL 

 Soc. Geol. France, ser. 3, vol. xi. p. 456. 



