HASEMAN, GEOGRAPHICAL DISTRIB UTION IN SO VTH AMERICA 85 



mation of the Brazilian Piano Alto. This cosmopolitan flora continued 

 to exist in the Mesozoic epoch, but the Gangamopteris flora, excepting 

 Glossopteris and Schizoneura, vanished with the close of the Permian. 

 In this remarkable fact, we have, I believe, part of the solution of the 

 Gangamopteris flora, i. e., it existed in Brazil only during the formation 

 of the Piano Alto and died out after this was completed (early Triassic). 



In this profound change of the ancient Brazilian topography produced 

 by the formation of the Piano Alto in the Permian inland basin, we have 

 the production of unfavorable environments which might have produced 

 the alleged glacial effects on the Gangamopteris flora and have caused 

 the absence of the cosmopolitan plants in the lower G-ondwana formation 

 of Brazil. This view is further strengthened by the fact that the shales, 

 etc., of the lower Gondwana formation have a different appearance and 

 chemical analysis from those of the higher formations in which the cos- 

 mopolitan flora are found. The cosmopolitan flora is always associated 

 with the production of large coal fields, and such conditions are not met 

 in the Gondwana formations of Brazil. It appears to me that it was 

 desiccation (perhaps not due to a lack of rainfall, but to its disappear- 

 ance in a sandy soil) and the blowing of sand into the Permian inland 

 basin, and not severity of climate (glacial), which produced the stunted 

 appearance of the early Gondwana flora. 



Several other objections can be raised against the use of Permian 

 glaciation as a factor which affected the distribution of the Permian 

 plants and reptiles of South America. In the first place, the writer does 

 not believe that the existence of glaciers in Brazil has been definitely 

 established. His experience with glaciation in North America and gla- 

 ciers in the Andes, taken in connection with observations on erosion in 

 the highlands and mountains of Brazil, has strongly suggested to him 

 that the Orleans conglomerates were not deposited by glaciers. In the 

 highlands of Piauhy and various places in Brazil, one can see both high- 

 land streams and extensive slanting surfaces over which gravel and 

 bowlders slide during heavy rains. The underlying surfaces and bowlders 

 are often scratched in a way which resembles glaciation. When pieces of 

 the scratched and polished surfaces are detached, segregated or not, as is 

 often the case due to less and greater amount of rainfall, and deposited 

 at a lower level, a "false moraine" and even false bowlder till is formed. 

 When such a mass of gravel, clay, bowlders, etc., becomes covered up and 

 pressed together by later erosion in little stratified or unstratified beds 

 (due to continual deposition and plasticity of the clay), it can easily be 

 mistaken for a glacial deposit. It can only be distinguished from glacial 

 deposits by means of truly faceted bowlders ; and inasmuch as faceted 



