16 



VEETEBKATA OF THE TEETIAEY, 



this formation the 

 retained.* 



According to 



Oregon, but Mr. King's name is the older, and must be 



Professor Condon, the Truckee formation of Oregon, on 

 the John Day River, rests unconformably on the 

 laminated beds containing Toxodium and fish 

 remains, which, as I have suggested on a pre- 

 vious page, may be an extension of the Amyzon 

 shales. These in turn rest on a formation of hard 

 laminated beds, which contain an abundance of 

 Calamites, which doubtless belong to the Triassic 

 or Jurassic period. The Truckee beds are, like 

 ^ the true White River, overlaid by the Loup Fork, 

 S, and this in turn by heavy beds of basalt. 



The fauna of the Tnickee presents some 

 g characters which distinguish it from that of the 

 o White River. These are, the absence of Hya- 

 £ nodon and Ischyromys and most of the Menodon- 

 J tidoe, and the presence of several genera of Canidce, 

 ■S FelidcE, and Bodentia. Many genera, and appar- 

 ently several species, were common to the two 

 epochs. 



THE LOUP FORK. 



This formation has now been studied in 

 many widely-separated localities in the region 

 west of the Mississippi River. It was discovered 

 by Dr. Hayden, whose collections furnished the 

 basis of Dr. Leidv's determination in 1858.+ It 

 was next observed by myself in Colorado in 

 18 73, J and twenty-one species wei*e determined ; 

 and, in the following year, I identified the 

 Santa F^ marls of New Mexico, already observed by Dr. Hayden, with the 



• Bnlletin U. 8. Geol. Sorv. Terra., v, p. 52. 



tSco Proc. Acad. Nat. 8ci. Phila., I^.V, p. 20, and Extinct Mammalia of Dakota and Nebraska. 



$ Bulletin of the U. S. Geol. Sorv. Torrg., No. 1, Jan., 1874. 



