14 RECORDS 



The discussion of the paper was confined chiefly to questions 

 regarding these methods and results. 

 Section adjourned. 



F. L. Tufts, 

 Sea'ctmy. 

 SECTION OF BIOLOGY. 



February io, 1902. 



Section met at 8:15 P. M., Professor Stratford presiding. 



The minutes of the last meeting of Section were read and ap- 

 proved. 



The following program was then offered : 



W. B. Scott, The Origin and Development of South 

 American Mammals. 



Summary of Papers. 



Professor Scott began by expressing his great obligation to 

 Dr. F. Ameghino, as also to Dr. Moreno, Director, and to the 

 Curators of the La Plata Museum, for their kindness in giving 

 him the freest use of their collections, and enabling him to 

 examine all the types of the Santa Cruz mammals. 



The fauna of every continent is made up of two elements, 

 the indigenous forms which were developed in that continent, 

 and the immigrants from other regions. In South America this 

 distinction is easy to draw, because of the remarkable series of 

 Tertiary deposits which are wonderfully rich in well-preserved 

 fossils. The Santa Cruz beds, which are referable to the lower 

 Miocene, contain an assemblage of mammals altogether different 

 from those of the northern hemisphere. The fauna consists of 

 Primates and Insectivora, very scantily represented, veiy nu- 

 merous Rodents (though all referable to the Hystricomorphs), 

 Marsupials, Edentates, and the peculiar South American hoofed 

 animals. The Edentates of this period represent the Gravi- 

 grada, Glyptodonts, and Armadillos, but no members of the 

 true sloths or Anteaters have yet been found, a lack of which is 

 probably due to climatic conditions. The Gravigrada, which 

 are very abundant, have forerunners of all the great Pleistocene 

 groups, but are, of course, much less specialized and are rel- 



