252 TEN years' progress in vertebrate paleontology 



But with South America a wide divergence of opinion exists as to the 

 time equivalence of its manmial faunae with those of the northern world. 

 This is not because of lack of evidence. Few faunae compare with those 

 of the Argentine Eepublic in numbers, variety, and perfection of ma- 

 terial. It is not because of lack of interdigitated marine formations; 

 hardly even in Europe are the relations of the marine and continental 

 succession so clearly displayed. It is rather because the faunae are so 

 remote geographically and zoologically from those of the northern world 

 that their real time equivalence becomes a matter rather of interpreta- 

 tion and inference than of direct evidence. The northern faunae, derived 

 from a common northern center, are represented on each side of it by 

 equivalent and closely related types. The southern faunae, if derived from 

 the north, are survivals lagging behind those of the northern world; if 

 derived from the south they will be more progressive than in the northern 

 world. Hence a southern fauna will be regarded as either older or 

 younger than its evolutionary equivalent in the north, according to the 

 theories held as to the source of the fauna. Herein apparently lies the 

 basis of the wide divergence of opinion that still exists regarding the true 

 age of the Argentine faunae. While this is most marked in the conti- 

 nental faunae it should be remembered that it is also true of the marine 

 faunae. 



Great progress has been made in the last decade toward accumulating 

 adequate data to solve this problem. Especially important are the collec- 

 tions secured by the Princeton and American Museum expeditions to Pat- 

 agonia, chiefly in the Santa Cruz formation, and studied and described 

 by Scott, Ortmann, Stanton, and Sinclair; the collections obtained by 

 the Paris Museum from the underlying formations, and described by 

 Gaudry, and the explorations of Santiago Eoth-"* (1908) for the La Plata 

 Museum. The recent work of Dr. F. B. Loomis for Amherst Museum and 

 of Bailey Willis for the Argentine government will also add largely to 

 the available data. The geological observations of Steinmann, Nordens- 

 kjold, and other geologists, and the paleontological studies of Cossmann, 

 Canu, Wilckens, Ameghino, Roth, von Ihering, and others likewise afford 

 information of the highest importance. 



These studies have sensed to fix authoritatively many of the data, 

 stratigraphic and morphologic, from which the problem must be solved. 

 The problem itself must still be regarded as an open one.-^ None of the 



=* Santiago Roth: Beitrag zur Gliedenmg der Sedimentablagerungen in Patagonien und 

 der Pampasregion. Neuen Jabrb. f. Mineral. Geol. u. Pal., Band xxvi. 1908. pp. 02-10r>. 



25 Le classement des couches patagoniennes a fait et fera encore, coiiler des flots 

 d'encre. Cossmann in Revue Critique de Paleozoologie, 1007, p. 181. 



