HAS EM AN, GEOGRAPHICAL DISTRIB UTION IN SO UTH AMERICA 29 



somewhat arid on .account of higher, sun*ounding older mountains, but 

 even if it had sufficient rainfall, on purely lithological grounds, a luxu- 

 riant vegetation and fauna would be impossible, because a sandy soil does 

 not retain the necessary constituents for a luxuriant growth of plants. 

 Besides, it appears more probable that unstable regions would produce 

 greater changes in living things than stable regions. Hence, not until the 

 Piano Alto was deeply eroded, could we expect to find a luxuriant growth 

 of vegetation and a complex fauna. Also, the Triassic Parana trap 

 which spread over much of the highlands of the states of Parana and Sao 

 Paulo of southern Brazil may have been an important factor in extermi- 

 nating and affecting the plants and animals, such as perhaps the G-ond- 

 wana flora and Permian reptiles which are discussed in the second part of 

 this thesis. 15 



EAST ANDEAN" SEA 



Several years ago, Professor Orton, Barrington Brown and others col- 

 lected marine or brackish water fossils mixed with fresh-water forms 

 along the Alto Eio Amazonas. 



The following is a list of the fossils which have been ascribed to Alto 

 Eio Amazonas by Gabb, Conrad, Etheridge, Woodward and Boettger: 



Anisotliyris tenuis Gabb 



carinata Conrad 

 obliquus Conrad 

 erectus Conrad 

 cuneatus Conrad 

 ovatus Conrad 

 hauxicelli Woodward 

 tumid a Etheridge 

 amizonensis Gabb 

 Neritina (Iscea) ortoni Gabb 

 pupa Gabb 

 puncta Etheridge 

 ziczac Etheridge 

 Hydrobia lintea Conrad 



conftisa Boettger 

 tricariiiata Boettger 

 (Dyria) gracilis Conrad 



Hydrohia dubia Etheridge 



Lacuna (Ebora) crassilabra Conrad 



(Nesis) bella Conrad 

 Hemisinus sulcatus Conrad 

 Melania tricarinata Etheridge 

 bicarinata Etheridge 

 scalaroides Etheridge 

 Dreissenia fragilis Boettger 

 Turbonilla ininuscula Gabb 

 Corbula canammnsis Etheridge 

 Meianopsis browni Etheridge 

 Cerithium coronatum Etheridge 

 Pseudolacuna macroptera Boettger 

 Assiminea crassa Etheridge 

 Bulimus linteus Conrad 

 Anodonta batesi Woodward 



Fragments of the following genera have been reported by Woodward: 

 Myliobatus, Fenella, Thracia, Lutria, Anodon, Unio, Nautica, Odon- 

 stomia. Boettger has also reported Serpula (Vermes) and Rajidum and 



13 It is to be noted here that similar Permian and Triassic continental deposits exist 

 in other parts of South America (Ceara, Brazil, San Laiis, Argentina, etc.) which are not 

 included in my Piano Alto, because they have been separated by marine deposits. 



