Later Extinct Flora* of North America, 



poplars, the leaves of which in other respects most resemble 

 these. The surface is. in many specimens, somewhat roughened, 

 as though in the living leaf it was canescenl ; also a common 

 character among poplars, but rare or unknown among maples. 

 The leaves of the maples are generally thin, and the network of 

 the tertiary nerves is remarkably fine and uniform, affording a 

 reliable generic character. This is visible in the leaves of all 

 the recent maples, and is beautifully shown in the impressions 

 of the leaves of A. pseudoplatanvs, given in Ettingshausen 

 and Pokorny's Physiotyjpia Plant. Austria, Taf. xvii., fig. LO, 



Among fossil species this perhaps resembles most P. leuco- 

 phylla (Foss. Flor. v. Gleichenberg Denkschrift, k. k. Acad.. 

 vol. viii., 1854, p. 177, Taf. iv., figs. ,; -10), but is much more 

 distinctly crenate-toothed on the margin. The teeth of P. 

 It ucophylla are either obsolete or remote and acute, making a 

 sinuate-dentate margin. 



Formation and Locality. Lignite Tertiary beds. Fort 

 Union, Dacotah. (Dr.Hayden.) 



Populu* Smilaci folia, (n.sp.) 



Leaves ovate, pointed, slightly cordate al the base; margins 

 finely and obtusely crenulated; nervation radiate, delicate, and 

 sparse; medial nerve straight, giving off only fine and scarcely per- 

 ceptible lateral nerves below, and two or three longer branches 

 near the Summit; tWO pairs of lateral nerves radiate with the 

 medial nerve from the same point at the base of the leaf; of these 



the lower two are small, nearly simple, and a rehed evenlj upward ; 

 the other two, nearly as Btrong as the mid rili, Bpring from the base 



at an angle Of about 25°, and, after diverging to the middle of the 

 leaf, curve upward toward the summit, Dear which they terminate 

 in the margins. These I at em 1 nerves supporl four or five simple or 

 pnee-forked branch ich given off exteriorly, which curve up- 

 ward, and terminate in the lateral margins. The tertiary nerves 

 are given off nearly at right angles from the secondaries, and form 

 a delicate polygonal or quadrangular network over the surface of 

 the leaf. 

 The lower pair of lateral nerves should properly be consid- 

 I a- branches of the larger ones, so that the leaf is more 



