506 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



16. QUERCUS DUBIA, 11. sp. 



Leaf ovoid in outline, unsyinmetrical ; margins strongly and remotely 

 toothed; teeth subacute or obtuse ; nervation delicate; midrib llexuous; 

 lateral branches, about six on a side, somewhat waved, branched, and 

 interlocking, and terminating in the marginal denticles; surface smooth, 

 consistence })robably somewhat coriaceous. 



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

 Collected by Dr. Hayden. 



17. QUERCUS SULLYI, n. Sp. 



Leaves ovate, pointed, wedge-shaped, or rounded at the base ; mar- 

 gins set remotely or closely, with acute, spiny-pointed teeth ; nervation 

 strong, somewhat flexuous ; lower pair of lateral nerves giving ofl' num- 

 erous branches, middle and u])per pairs simple below, foiled at the 

 summit. 



Formation and locality. — Burned shales over lignite beds, Fort Ber- 

 thold, Dakota. Collected by S. M. Rothhammer, on the expedition of 

 General Alfred Sully, U. S. A. 



18. QUERCUS CASTAXOIDES, U. sp. 



Leaf linear-lanceolate, acute, G inches long by 1 inch broad; margins 

 remotely and somewhat irregularly set with coarse, in some cases spi- 

 nous, teeth; nervation strong; midrib straight, sharply defined ; lateral 

 branches unequally spaced, simple, forked near the extremity, terminat- 

 ing in the margiiial denticles. 



Formation and locality. — Eocene Tertiary, Green River, Wyoming. 

 Collected by Dr. C. A. White. 



19. POPULUS POLYMORPHA, n. sp. 



lisaves petioled, ovate, rounded or slightly wedge-shaped at the base, 

 acute or blunt-pointed at the summit ; margin coarsely and irregularly 

 crenate, dentate, or crenate-deutate ; nervation strongly marked, 

 pinnate ; in the more elongated forms, about eight branches on each 

 side of the midrib given oft' at an acute angle ; in the broader forms 

 the lower nerves issue at nearly a right angle ; the upper ones at an 

 angle larger than in the preceding form. 



Formation and locality. — Tertiary strata. Bridge Creek, Oregon. Pro- 

 fessor Condon. 



20. POPULUS ROTUNDIFOLIA, 11. sp. 



Leaves of small size, rarely more than an inch in diameter, approxi- 

 mately circular in outline, either quite round or transversely or longi- 

 tudinally elhptical ; slightly wedge-shaped at the base, and decurrent 

 on the long ])etiole ; basal margin entire ; upper half of leaf coarsely 

 crenate, dentate, and usually short pointed at the summit; nervation 



