ENVIEONMENT OP THE TITANOTHEEES 



59 



Figure 41. — Eocene and lower Oligocene mammalian life zones in eleven typical correlated areas in New 

 Mexico, Colorado, Utah, Wyoming, South Dakota, and Montana, located as shown on the general geologic 

 map (fig. 35) 



Arranged by Osborn (1919) after original studies made in the field, chiefly by Granger, but also by Hatcher (Oligocene), Hills, Peterson, and 

 Gidley (Eocene) . The 16 Icnown life zones numbered 1 to 15 and 17 are indicated in the diagram by darlc horizontal lines. The nonfossiliferous 

 areas are indicated by light oblique lines. These life zones and sections also correspond with the detailed geologic sections in this chapter. 

 The United States Geolojical Survey classifies the Lance formation as Tertiary (?), Eocene (?). The author of this monograph regards it 

 as Cretaceous. 



