82 THE LATER EXTINCT FLORAS OF NORTH AMERICA. 



toothed; nervation strong; lateral nerves diverging at an angle of about 

 50 degrees in five to six pairs branching toward the summit, and inosculating 

 along the margins; tertiary nerves strong, leaving the secondaries nearly 

 at right angles, much branched and anastomosing to form a coarse and 

 irregular network." 



Collected by Dr. F. V. Hayden. 



In its general form this leaf has a striking resemblance to Planera 

 Ungeri Ett. (Abhandl. k. k. geolog. Reichsanstalt. Wien, Vol. II (1851), Foss. 

 Fl. Wien, p. 14, PI. II, figs. 5-18), Ulmus Zelkovafolia Ung. (Chlor. Prot., 

 p. 94, PL XXIV, figs. 7-13; XXVI, figs. 7, 8), but it is apparently con- 

 siderably smaller, narrower, and more coarsely toothed. 



Formation and locality: Tertiary (Fort Union group). Fort Union, 

 Dakota. 



Planera nervosa Newb. 



PI. LXVII, figs. 2, 3. 

 Proc. IT. S. Nat. Mus., Vol. V (March 21, 1883), p. 508. 



"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." 



Collected by Dr. C. A. White. 



The most striking feature in these leaves is their strong, crowded, reg- 

 ular nervation, from thirteen to nineteen nearly equidistant simple nerve 

 branches issuing from either side of the midrib. The nervation is equally 

 regular in P. longifolia, Lesq., Tert. FL, p. 189, PL XXVII, figs. 4-6; this 

 volume, p. 81, PL LVIII, fig. 3, but is lighter, and the marginal dentation 

 is coarser, the teeth more obtuse. 



Fig. 4, on Lesquereux's plate cited above, resembles more the leaves 

 before us and apparently belongs to a species distinct from the other 

 two leaves with which it is there associated, possibly to this one. The 

 leaves of P. longifolia are found in great abundance at Florissant, Colorado, 

 and they are so much alike that there is no difficulty in separating them 

 from other described species; while in the localities where the leaves of 

 P. nervosa occur there are none which have the few long, horizontal^ cut 

 teeth of P. longifolia. Hence while there is considerable resemblance in 



