62 THE MAMMALIA OF THE DEEP RIVER BEDS. 



advance of its contemporaries in Europe, just as the American ruminants in several 

 horizons lag behind their contemporaries of the Old World. Further, to regard the 

 Loup Fork as Pliocene involves the assertion that Procamelus in America was con- 

 temporary with Camelus in Asia, which, seeing that the camel series is of American 

 origin, is most improbable. 



Of the European faunas, that of Sansan and Simorre offers the best analogy 

 with that of the Deep River beds. In both continents this horizon is marked by the 

 first appearance of the mastodons, and, since the Proboscidea would seem to have 

 originated in neither Europe nor America, but to have reached both regions by 

 migration, this fact is significant. Anchitherium, in the restricted sense in which I 

 have used that word, is likewise common to both, and, as this genus has a very 

 restricted range in time, it is a most important fossil. Blastomeryx is exceedingly 

 like the Sansan species of Palceomeryx, though more primitive in some respects. No 

 stress can be laid upon the supposed Aiwphicyon and Procervulus of the Loup Fork, 

 as these names are incorrectly given to the American forms. 



If Dall's contention, that North and South America were not united until the 

 close of the Miocene (No. 12, p. 21), be confirmed, the Loup Fork will necessarily 

 be referred to the Pliocene, as is indicated by the occurrence in those beds of the 

 glyptodont genus, Oaryoderma Cope, a South American type, though the genus 

 itself has not yet been obtained in that continent. But the evidence for the date of 

 the elevation of Central America and the Isthmus of Panama is by no means con- 

 clusive. Grabb's statement is to the effect that " The communication between the 

 Atlantic and Pacific in the region of Costa Pica was interrupted in the Pliocene or 

 subsequent to the deposition of the mass of the Miocene strata " (italics mine) (quoted 

 in Dall and Harris, No. 12, p. 188, from Gabb's MS. report). This is quite compati- 

 ble with the view that the connection of the two continents was made before the end 

 of the Miocene. If we may provisionally regard the Deep River beds (upper series) 

 as equivalent to those of Sansan and Steinheim, the John Day would consequently 

 be about equivalent to the lower Miocene of St. Gerand le Puy, though probably 

 somewhat older, and the White River to the beds of Rouzon or the "Marnes lacus- 

 tres." The term Oligocene has not been found necessary in this country, the line 

 between the Uinta and White River beds being a clear and convenient demarcation 

 between the Eocene and Miocene. Nevertheless, much confusion and incorrect rea- 

 soning have resulted from calling the White River simply Miocene. The presence of 

 such genera as Hyxnodon, Hemijjsalodon, Mesonyx, Elotherium, Hyopoiamus, etc., 

 sufficiently proves these beds to be more ancient than the true Miocene of Europe, 



