EXPLANATION OF PLATES. 



Column 3. — Fore-arms, or radii and ulnae, showing the change in 

 the latter and the soldering of the bone at last closely to the radius. 

 Column 4. — Legs, or tibiae and fibulas. 

 Column 5. — Side view of upper molars. 

 Column 6. — Crowns of upper molars. 

 Column 7. — Crowns of lower molars. 



PLATE XL 



Illustrations of Brain-growth during the Cenozoic, after Marsh. — 



Page 508. 



Figure 1. — Outline of skull and brain-cavity of Dinoceras (Eo- 

 cene). 



Figure 2. — Outline of skull and brain-cavity of Brontotherium 

 (Miocene). 



Figure 3. — Outline of skull and brain-cavity of the Horse (Recent). 



PLATE XII. 



Diagram of Strata, arranged by Marsh, to show the succession in 

 Vertebrate Life in America. 



