398 OKIGIN OF LIFE IN AMEEICA 



Naturally his views gave rise to a considerable amount of 

 discussion jand criticism among geologists and palaeontolo- 

 gists ; and many visited the scenes of these startling dis- 

 coveries. Almost all of them felt convinced that Dr. 

 Ameghino had wrongly interpreted the age of the deposits 

 alluded to. They thought that the fossiliferous beds described 

 must be much more recent than Dr. Ameghino supposed, and 

 that at any rate South America was certainly not the source of 

 all the mammalia. One of the richest of the deposits exposed 

 in different parts of Patagonia, especially in the region of the 

 Santa Cruz river, and hence spoken of as the " Santa Cruz 

 beds," is considered by Dr. Ameghino as of Upper Eocene 

 and Lower Oligocene age. Almost all other authorities believe 

 them to belong to the Miocene. The latter view seems to be 

 strengthened by the results of the study of the marine shells 

 contained in beds of similar age which were pronounced by 

 Dr. Ortmann * to be of Miocene Age. As Professor Scott f 

 expresses the opinion that Dr. Ortmann has clearly demon- 

 strated the Miocene age of the Santa Cruz beds, I should like 

 to direct attention to a more recent work dealing with this 

 problem. Its author, Dr. von Ihering,J has made a special 

 study for many years past of the marine mollusks of South 

 America. Hence his opinion is of particular value. After 

 a long and careful study of a larger series of fossil mollusks 

 than was available before, he came to the conclusion that 

 the marine Cretaceous deposits of Patagonia pass very gradu- 

 ally into those of the next formation, which is the one 

 described by Dr. Ortmann, the latter scarcely containing 

 five per cent, of living species. He is inclined on that 

 account to agree with Professor Ameghino as to the Eocene 

 and Oligocene age of these marine beds, and thus indirectly 

 with his general scheme of correlation. Dr. von Ihering's 

 arguments appear to me more convincing than those of Dr. 

 Ameghino's opponents, and I shall therefore adhere to the 

 latter's nomenclature of the Argentina deposits. Not only 

 has Dr. von Ihering adopted Dr. Ameghino's views, they 



* Ortmann, A. E., "Princeton University Expedition," Vol. IV., 

 p. 317. 



t Scott, W. B., "Mammalian fauna of Santa Cruz," p. 241. 

 | Ihering, H. von, "Mollusques fossiles de PArgentine," p. 95. 



