224 W. D. Mattliew — Fossil Vertebrates and 



(4) Preliminary stages of diastrophic epochs are 

 marked by (a) reduction of the marsh f annas to a limited 

 number of highly specialized survivors, (b) invasion of 

 the lowland by the regional upland fauna, (c) appearance 

 of a few forerunners (mobile t^^es) of a great invasional 

 fauna from the center of dispersal. 



(5.) Culmination of diastrophism is marked by the 

 maximum of new invading types from the more central 

 regions, partial or complete extinction of the autochthonic 

 faunas, and wide dispersal of identical fauna of upland 

 adaptation. 



(6.) Dying stages of diastrophism are marked by par- 

 tial readaptation of the new fauna to lowland or marsh 

 type, by its parallel evolution in isolation in different 

 regions. Survivors from a previous submergence stage 

 may re-expand, or may become extinct as unable to com- 

 pete with the expanded new fauna. 



(7.) It is unnecessary here to dis-cuss the effect of 

 oceanic or climatic barriers in modifying this sequence. 



In accord with the above h^^pothesis the post-Senonian 

 formations are viewed as representing the earlier stages 

 of a period of world-wide diastrophism which culminated 

 at the end of the Paleocene, the Eocene being an epoch 

 of decreasing diastrophism and isolation faunas. The 

 Judith fauna is the Cretaceous marsh fauna in the climax 

 of its prosperity, the Edmonton and Lance are stages 

 leading to its extinction. The Puerco represents the 

 regional upland fauna expanding and invading the low- 

 land, the Torrejon-Fort Union a later stage of the same 

 local invasion. The creodonts are regarded as forerun- 

 ners of the great invasion from the center of dispersal 

 (?Asia) which culminates in the Wasatch, and as new- 

 comers in the region in the Puerco. ^^ 



The dispersal of terrestrial faunas affords a measure 

 of the intensity of world-wide 'diastrophism. The culmi- 

 nation of diastrophic movements in Colorado or in West- 

 ern Europe may not, probably did not, coincide with the 

 maximum intensity of the general movement. But if we 

 are to use diastrophism as a logical basis for geologic 

 time divisions, it is the general maxima and not local 



^^ The Casamayor fauna of South America is regarded as of Eocene age, 

 derived from a Cretaceous upland fauna of North America in which Carni- 

 vora had not yet appeared. Hence the absence in it of true Carnivora and 

 development of marsupials to take their place. 



