EXPLANATION OF PLATE I. 



Fig. 1. Oreodon superbus: 



A side view of a skull, with the base of the cranium invested in the matrix. Specimen ob- 

 tained by Eev. Thomas Condon on John Day's River, Oregon. One-half the natural size. 



Figs. 2,3. Megacerops coloradensis : 



Fig. 2. Upper view of tbe nasal extremity of the face with a pair of horn-cores. One-half 



the natural size. 

 Fig. 3. Front view of the same specimen 



