HASEMAN, GEOGRAPHICAL DISTRIB UTION IN SOUTH AMERICA 91 



In this connection, great emphasis must be placed on the stability of 

 the Serra do Mar and the surrounding Gondwana formations of southern 

 Brazil when contrasted with the violent geological transformations which 

 the possible regions of migration through North America have under- 

 gone. In fact, I firmly believe that no traces of the Gondwana flora 

 would remain in southern Brazil, if this region had undergone the same 

 radical changes as the possible routes of migration through North 

 America. 



The mere fact that the Gangamopteris flora appeared to live undei 

 rather unfavorable conditions in which little coal was deposited is very 

 important. Could not similar Gondwana environments have existed dur- 

 ing a brief period in the northern hemisphere, and might not these en- 

 vironments have been obliterated by the post-Permian changes of the 

 North American topography ? It appears that the stability of the Plana 

 Alto has saved the Gondwana flora of southern Brazil. 



Professor Branner states in his "Geologia Elementar" that marine 

 fossils are found associated with the deposits containing Stereosternum 

 in the State of Sao Paulo. These fossils are all lamellibranchs, which 

 include such Permian genera as Schizodus, Myalina and Conocardium, 

 and other genera which are equally well considered as Triassic. This is 

 the only known invasion of the sea that entered the Gondwana region o£ 

 Brazil during the Permian and subsequent periods. Hence the Gond- 

 wana of Brazil has been extremely stable. This indicates very great 

 altitudes along the eastern side of South America during the Paleozoic 

 epoch. These great altitudes are needed to build the great Piano Alto 

 and to account for the existing altitude of Serra do Mar after the vast 

 ages of post-Permian erosion. 



If the Gangamopteris flora entered South America from North Amer- 

 ica, one may ask why it is not found in northern South America. 

 Whether it came from North America or not, I believe that it existed in 

 northern Brazil, because the Permian inland basin was continuous from 

 southern Brazil to the Guianas. In fact, Psaronius has recently been 

 found by Dr. Lisboa at Floriana on Eio Parahyba do Norte. All this 

 part of South America is very imperfectly known and awaits explora- 

 tion. If the Gondwana flora is later found in northern South America, 

 about 3,000 miles of a northern distribution will be abridged and the 

 remaining distance will not be many times greater than a possible south- 

 ern one. Hence due allowance must be made not only for the imperfec- 

 tion of the fossil record but also for the lack of sufficient exploration. 

 When this is done, a northern distribution of the Gondwana flora is not 

 altogether impossible. 



8 NY 



