THE EOCENE OF EUROPE AND NORTH AMERICA 



87 



of life from the beginning of the Eocene to the end of Ohgoeene times, as 

 shown in the diagram (Fig. 10) on page 49. 



Fig. 21. — Chief Fossil Mammal Deposits of Western North America. PT. Puereo and 

 Torrejon, N. Mcx. BH. Big Horn Basin, Wyo. W. Typical Wasatch, Evanston, Wyo., and 

 Utah. WE. Wind River, Wyo. H. Huerfano, Col. B. Bridger. Wyo. WK. Washakie, 

 Wyo. V. Uinta, Utah and Col. 12. Swift Current Creek, Assiniboia. 10. Pipestone 

 Creek, Mont. 2. Typical White River and Ro.sebud, S. Dak. 1. White River, Monroe 

 Creek and Harrison, Nebr. 4. Horsetail Creek, Cedar Creek, Pawnee Creek and Martin 

 Canyon, Col. 7. John Day, Mascall and Rattlesnake, Greg. 8. Fort Logan and Deep River, 

 Mont. 11. Flint Creek, Mont. 6. Panhandle, Clarendon, Blanco and Rock Creek, Tex. 

 17. "Nebraska" and underlying bods, Nebr. 5. Santa Fe marls, N. Mex. 9. Madison 

 Valley, Mont. 3. Republican River, Kan. 14. Snake Creek, Nebr. 18. Silver Lake, Oreg. 



It was believed formerly that each of these great mountain basins con- 

 tained a lake and that the deposits consequently were lacustrine, but the 

 'lake theory' has gradually given way to the theory that these were princi- 



