322 H. F. OSBORX CLOSE OF CRETACEOVS AND OPENING OF EOCENE 



trial fauna is known in Europe corresponding with the Danien time epoch 

 or with the "Xance" fauna of Xorth America. 



The very ancient Paleocene formations of northern Europe, including 

 the problematic Montien epoch and the well defined Thanetien marine 

 pha^e, are along the sea borders, and consequently are unfavorable to the 

 preservation of mammalian life. They contain no -dinosaurs or mosa- 

 saurs. Among these are the Sables de Rilly, seashore sands containing 

 many marine mollusks which are similar to those in the Sables de Bra- 

 cheux, another Paleocene fonnation. In France, however, as long ago as 

 1841, one fluviomarine formation yielded a single mammal, Arctocyon 

 primcBvus, in beds correlated in time with the Thanetien. At a slightly 

 subsequent period of Thanetien time a river-borne formation includes 

 the celebrated mammalian faaina of Cernay and the single surviving 

 Cretaceous reptilian tj^je Champsosaurus. 



Without exception it may be said that all tlie paleontologists of Europe 

 have considered the Cretaceous as the period of the final extinction of tlie 

 terrestrial dinosaurs and the marine mosasaurs ; and they have similarly 

 defined the Paleocene not only by. its new forms of marine mollusca, but 

 by the survival of the characteristic plagiaulacid mammals of the Sfezo- 

 zoic and "the first general appearance of a primitive mammalian land 

 fauna, which broadly corresponds with a similar Puerco-Torrejon-Fort 

 Union fauna in Xorth America. 



The discussion to which we are devoting this session of the Paleonto- 

 logical Society is of great interest and importance because a number of 

 eminent American paleobotanists and geologists, as well as certain inver- 

 tebrate paleontologists, are of the opinion that the close of Cretaceous 

 time occurred long before the extinction of certain great families of ter- 

 restrial dinosaurs, and that as a consequence the opening of Eocene time 

 is not the beginning of the so-called Age of Mammals, but embraces a 

 prolonged closing chapter in the Age of Reptiles. 



The various kinds of evidence which may be adduced in favor of tliis 

 interpretation of the succession of phenomena in Xorth America will be 

 presented by Dr. F. H. Knowlton, who. firstly, will demonstrate that 

 paleobotany does not indicate any sharp line of demarcation between the 

 Upper Cretaceous ('T.ance") and Lower Eocene, and, secondly, he will 

 point, out the evidence, which is accepted by a considerable number of 

 American geologists, for the belief that there is widespread diastrophism 

 occurring at a certain period long before the close of the Age of Eeptiles. 

 This diastrophic movement is believed by Doctor Knowlton to correspond 

 with the close of Cretaceous and opening of Eocene time. It occurs long 

 before the close of the Age of Eeptiles. 



