HASEMAN, GEOGRAPHICAL DISTRIB UTIOX IX SOUTH AMERICA 11 



Rio de Janeiro. Sao Paulo, Para, Montevideo and Buenos Aires, and 

 among my other South American friends, to Eicardo Krone of Iguape, 

 John Gordon, Alipio Miranda Ribeiro and Carlos Moreira of Rio de 

 Janeiro, Dr. Jappa Assii of Bahia, Rudolfo von Ihering of Sao Paulo, 

 Dr. Frank Davis and Feliciano Simon of Corumba and Dr. Snetlager of 

 Para. 



Among my preceptors, I record gratefully my indebtedness to Dr. 

 Eigenmann, with whom I carried on my special studies in the University 

 of Indiana; to Dr. A. E. Ortmann while I was in Pittsburgh, and to 

 Drs. Dean, Grabau. Gregory and Hussakof while at Columbia, where a 

 scholarship and the income of the Dyekman Fund for 1910 were gener- 

 ously granted me. 1 



The living and extinct fauna and flora of South America possess in 

 certain eases, at least, a close genetic relationship with that of the south- 

 ern portion of the eastern hemisphere. This remarkable fact has led to 

 a prevailing view that South America was cnce connected with some 

 point of the eastern hemisphere. This view assumes that the closely 

 related fauna and flora are descended from common ancestors which 

 existed in the old land mass or continent to which the name Gondwana 

 has been applied. 



In this thesis, it will be my effort to show that at least certain, if not 

 all, elements in the fauna and flora of South America have evolved from 

 forms which have from time to time been introduced from the northern 

 hemisphere. In this view, I have brought together not only materials 

 from references and from the laboratory but also data obtained during 

 two and one half years of active field work. The amount of this ma- 

 terial altogether will be sufficient, I think, to demonstrate that South 

 America was never connected with the eastern hemisphere by a hypo- 

 thetical southern and sunken mass of land. 



In the preparation of my paper, I have been obliged to omit numerous 

 data and assorted faunal lists whose bearing has been more or less direct 

 upon the present theme — in the latter cases since I am convinced that 

 the lists do not explain distribution unless accompanied by detailed ob- 

 servations upon the geology and the environmental conditions of the 

 country considered. Hence I have been led to divide my thesis into two 

 parts. In the first of these, we picture the past and present environ- 

 ments in which the fossil and existing animals lived. In the second, we 

 deal with the changes through which these animals and their ancestral 

 stocks have undergone after arriving in these environments. 



1 The geographical names are spelled as they are in their respective countries. I have 

 also used the old -way of spelling such words as "Silurian'' instead of "Siluric." I have 

 also omitted marks of accentuation and other similar marks. 



