508 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 

 25. UlMUS GEANDIFOLIA, 11. sp. 



Leaves large, 10 ceutiiueters long by 8 centimeters wide, ovate, often 

 imsyin metrical ; nervation strong, regular; midrib straight; lateral 

 nerves, about thirteen on each side, strong and simple, except at sum- 

 mit, where they give ott' numerous branches; margins sometimes entire 

 at base, but oftener .simply serrate-dentate throughout. 



Formation and locality. — Tertiary strata. Tongue Eiver, Wyoming. 

 Dr. Ilayden. §^ 



2G, Planeea variabilis, n. sp. 



Leaves lanceolate to broad ovate ; usually unsymmetrical, petioled ; 

 summit acute, sometimes long-pointed ; base rounded or wedge-shaped; 

 margins coarsely crenulate-dentate, or serrate, with remote, appressed 

 teeth; midrib straight, strong; lateral nerves delicate, frequently alter- 

 nating stronger and finer, gently arched upward, terminating in the 

 teeth of the border ; the finer intermediate ones sometimes fading out 

 before reaching the margin. 



Formation and locality. — Eocene Tertiary, Green River Station, Wyo- 

 ming. Collected by Dr. C. A. W^hite. 



27. Planeea nervosa, n. sp. 



Leaves ovate or lanceolate, pointed, wedge-shaped, or rounded at the 

 base, petioled ; margins set with coarse, appressed teeth ; nervation 

 strong, crowded, regular; lateral nerves simple, parallel, terminating 

 in the teeth of the margins. 



Formation and locality. — Eocene Tertiary strata, Green River, Wyo- 

 ming. Collected by Dr. C. A. White. 



28. Planeea crenata, n. sp. 



Leaves oblong, ovate; short petioled, 5 centimeters long by 25 milli- 

 meters wide ; base rounded ; summit blunt pointed ; margins coarsely 

 crenate ; nervation simple, delicate, six simple branches on each side of 

 the midrib terminating in the crenations of the margin. 



Formation and locality. — Tertiary strata, Tongue River, Wyoming. 

 Collected by Dr. Hayden. 



29. Betula angustifolia, n. sp. 



Leaves jietioled, oblong-lanceolate, 3 inches long by 1 inch wide ; 

 wedge-shaped or slightly rounded at the base, acuminate at summit; 

 margins finely serrate below, coarsely and doubly serrate above ; nerves 

 slender, about eight branches on each side of the midrib. 



Formation and locality. — Miocene ? Tertiary strata. Bridge Creek, 

 Oregon. Collected by Prof. Thomas C -ondon. 



30. Betula iieterodonta, n. sp. 



Leaf 2 to 4 inches in length, long petioled, ovate, acuminate, rounded 

 at the base; margins coarsely and irregularly serrate, the priu- 



