PLATE LX 



Upper Dentition of Limnohyops and Palaeosyops 

 Illustrating three stages in the evolution of the premolars. (See pp. 306-336.) Drawings by E. S. Christman. Natural size 



A, Limnohyops prisons, type (Am. Mus. 11687), Grizzly Buttes West, Bridger Basin, Wyo., level Bridger B 2; pi-m'. In this species 



the second, third, and fourth premolars are in a relatively low stage of evolution. 



B, Palaeosyops leidyi, type (Am. Mus. 1544), Bridger Basin, Wyo., level Bridger C 4(?), i'-m'. In this species the premolars are 



in a more advanced stage of evolution. 



C, P. copei, type (Am. Mus. 1170^,- Henrys Fork, Lone Tree, Bridger Basin, Wyo., level Bridger D 3, pi-m^, drawing reversed. 



In this species the premolars are in a very advanced stage of evolution. 



