1902.] Matthew, New Miocene Canidce. 287 



present and past distribution, originating in North America, 

 spreading to South America and Asia, and becoming extinct in 

 their old home while still surviving in the two widely separated 

 districts to which they had wandered. 



In this as in other cases the writer desires to guard against 

 expressing any belief that the evolutionary series worked out 

 in various lines represent the actual species through which 

 descent has occurred. They represent indeed the history of 

 the evolution of certain parts ; they may in some cases be not 

 far from the direct line of descent. But it appears probable 

 that each ' stage ' represents in most cases a migration rather 

 than a mutation of species. Believing that the principal 

 causes of the evolutionary changes among the Tertiary mam- 

 malia lay in the secular world-wide alteration in climatic and 

 geographic conditions, it seems improbable that in any given 

 locality a change in the fauna occurred directly without a 

 change in the area over v/hich the species flourished. It 

 seems much more likely that most of the changes in fauna in 

 a locality were due to successive waves of migration, setting 

 out from the region in which the new climatic conditions first 

 appeared. This would involve in general a succession of 

 waves of migration spreading from the north into America on 

 one hand, Europe, southern Asia, and Africa on the other, 

 differentiating to some extent as the separation increased, and 

 driving the older faunas southward before them. Hence the 

 Tertiary aspect of so large a part of the South American and 

 African faunas, and hence the primitive aspect of forest faunas 

 in general, the new conditions of cold and arid climate which 

 culminated in the Glacial Epoch involving the spread of open 

 plains, and diminution of the forest areas. 



Amphicyon americanus Wortman. 



Amphicyon aynericanus Wortman, Amer. Joum. Sci., Vol. XI, 201, 

 Sep. Jan. 25, March, 1901. 



This species is of moderate size in the genus and of rather 

 primitive character, in some respects approaching the species 

 of the European Oligocene {A. lemanensis , etc.). Dr. Wort- 

 man gives the following measurements : 



