KEY TO PLATE I. 



PT — Puerco, Torrejon, and Wasatch of San Juan 



basin, New Mexico Basal and lower Eocene. 



BH — Wasatch of Bighorn Basin, Wyonning Lower Eocene. 



W — Wasatch (typical), Evanston, Wyoming Lower Eocene. 



WR — Wind River, Wyoming Lower Eocene. 



H — Huerfano, Colorado Lower and middle Eocene. 



B — Bridger, Wyoming Middle Eocene. 



WK — "Washakie," Wyoming Middle and upper Eocene. 



U — Uinta, Utah Upper Eocene. 



12 — White River deposits along Swift Current Creek, 



Assiniboia, Canada Lower Oligocene. 



ID — White River deposits along Pipestone Creek, 



Montana Lower Oligocene. 



2 — Typical White River and Rosebud, South Dakota.. Oligocene and Miocene. 

 I — White River, Monroe Creek, and Harrison, 



Nebraska Oligocene and Miocene. 



4 — Pawnee Buttes section (" Pawnee Creek," " Martin 



Canyon," "Cedar Creek," "Horsetail Creek"), 



Colorado Oligocene to middle Miocene. 



7 — John Day, Mascall, and Rattlesnake, Oregon Oligocene, Miocene, and Pliocene. 



8 — "Fort Logan" and Deep River, Montana Lower and middle Miocene. 



II — " Flint Creek," Montana Middle Miocene. 



6 — "Panhandle," "Clarendon," Blanco, and "Rock 



Creek," Texas Miocene to Pleistocene. 



17 — "Nebraska" and underlying beds, Nebraska Miocene. 



5 — "Santa Fe marls," New Mexico Upper Miocene. 



9 — "Madison Valley," Montana Upper Miocene. 



3 — "Republican River," Kansas Lower Pliocene. 



13 — "Archer," Florida Lower Pliocene. 



14 — "Loup River," Nebraska Upper Pliocene. 



18 — Silver Lake, Oregon Lower Pleistocene. 



15 — Ashley River, South Carolina Pleistocene. 



16 — Port Kennedy, Pennsylvania Middle Pleistocene. 



19 — Potter Creek cave, California Middle Pleistocene. 



20 — Conard fissure, Arkansas Upper Pleistocene. 



