BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 25, pp. 321-324 SEPTEMBER 15, 1914 



PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



CLOSE OF THE CEETACEOUS AND OPENING OF EOCENE 

 TIME IN NOETH AMEEICA ^ 



BY HENRY FAIEFIELD OSBORN 



{Presented before the Paleontological Society December SI, 1913) 



In introducing this symposium on a critical point in geologic time 

 emphasis must first be laid on the fact that the Periods were defined dur- 

 ing the last century by European paleontologists, and that American 

 events can be dated only by comparison of American with European 

 faunas and floras, unless simultaneous and world-wide diastrophic move- 

 ments can be demonstrated to have occurred. 



The demarcation between the Cretaceous and the Eocene periods of 

 Europe rested first on the work of Deshayes on the extinct molluscan 

 fauna of the Paris basin. It gradually developed in definition and clear- 

 ness under Lyell, D'Orbigny, Mayer, and Eymar. Gradually also verte^ 

 brate reptiles and mammals entered into the problem, and the formations 

 along the northern coast of Europe and Belgium, with their contained 

 marine fossils, served to define the Mcestrichtien stage (Dumont, 1849), 

 while in the north another late Cretaceous phase typified, the Danien stage 

 (Desor, 1846). According to Haug (1912), the Danien overlies the 

 Mcestrichtien concordantly, and thus closes the Cretaceous period. The 

 fauna is purely marine and exclusively Cretaceous. Some authors also 

 place the overlying Montien in the Cretaceous. 



The Mcestrichtie^i as exposed in Belgium includes a rich reptilian 

 fauna, which comprises several kinds of mosasaurs, great marine turtles, 

 iguanodont dinosaurs, and their enemies, the carnivorous dinosaurs. This 

 is our last view of the dinosaur life of Europe. The Mcestrichtien fauna 

 has not been closely correlated up to the present time with an American 

 fauna. According to Williston, it is subsequent to any known American 

 mosasaur fauna, and this author regards the Mcestnchtien as a lower 

 phase of the Danien. It is to be noted also that no late Cretaceous ten-es- 



1 Manuscript received by the Secretary of the Geological Society June 12, 1914, 

 This paper is an introduction to the symposium on this subject held at the Prince- 

 ton meeting of the Society December 31, 1913, and January 1, 1914. 



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