. Equus 1 F .,-,1,. 



.4 i &). Toptr*.. AV,.*.,. 



* PliouippU! H.-.1-. 

 



' 



Miobippus Beds. 



Miotitppui, I>mratlitri<im, 



Oreodou Beds. 



Edcnuten, ff^mudon, 



Brontotheriuin Beds. 



.Vf.oAip;""- .VmodM. JH^IWrnoi. 



Uipliicodou Beds. 



kpiklpp**. Amiwxtv*. 



Dinoceras Bed*. 



Tinottrat, Vintatlaritim, l.imn:,l<i,v*. 

 Oruhipjtut. Utlaltttl, (Wolu>Mr<i 



Corypliodon Bedx. 



Evhippiu. Monkttn. Cirnlvorw, tnjul.iw. Tlllwlo 

 berpeotl. 



I.iuniie 8eriex. 



Pteranodon Bed*. 

 Birdi with Two. Iktptromit, 



Dakota Group. 



Atlaiitoeauru.x Beds. 

 Uinooura, .4pa(uMnu. 

 plotaurvi 



urtn. .Ynlir Tuflr. W. 



Connecticut River Bed. 



First Mmuim.ls (MinupUli). 

 Dloomur Foot-priQlu. Amphisaurui. 

 CraeodilM 



Coal Measures. 

 Flm Rtptilri (?) 



Sub-cari>oniferoU8. 

 Pint known Amphibluu (Ubyrinlhodonra). 



Schoharie Grit. 

 Firat known FUh. 



Upper Silurian. 

 Lower Silurian. 



Primordial. 



Huronjan. 



No Vertebrate* known. 



FIG. 302.-Section of theearth's crust, to illustrate vertebrate life in America. 

 (After Marsh.) (From Le Conte's Geology, American Book Co., Publishers.) 



393 



