54 THE LATER EXTINCT FLORAS OF NORTH AMERICA. 



interspaces are filled with a labyrinth of anastomosing veins, forming a 

 very different network from that of Populus. 



The marginal serration of the present species would seem to have been 

 much like that of the leaves of the living P. tremuloides, but still finer, 

 while the size of the leaf was considerably larger. 



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

 Dakota. 



Populates elegans Lesq.? 



PI. VIII, fig. 3. 



Am. Journ. Sci., Vol. XL VI (July, 1868), p. 94. 



Note. So identified by Dr. Newberry, as indicated by memorandum on the 



margin of the plate. — A. H. 



Formation and locality: Cretaceous (Dakota group). Fort Harker, 



Kansas. 



Salix angusta Al. Br.? 

 PL LXV, fig. 2. 



In Bruckm. "PL Oening. Foss." Wiirtemb. Naturwiss. Jahresh. (1850), p. 229. 

 S. angustifolia Al. Br., inBuckland, Geol. and Mineral., p. 512 (1837). J 



A very narrow-leaved willow; is exceedingly common in the Green 

 River beds, some slabs of the rock being quite covered with the leaves. 

 These are narrow, lanceolate, tapering gradually to a long and strong 

 petiole and to a long, narrow, and acute point above. The margins are 

 entire and sharply defined, the midrib strong, the lateral nerves numerous 

 and fine. 



In general form these leaves agree very well with the excellent figures 

 of Salix angusta, given by Heer in his Fl. Tert. Helv., Vol. II, p. 30, PI. 

 LXIX, figs. 1-11, but the base is in our specimens narrower, so much so 

 that the blade seems to be decurrent on the petiole. The leaves from Green 

 River apparently represent the same species as that figured by Lesquereux, 

 (Tert. FL, p. 168, PL XXII, figs. 4, 5) but perhaps not that shown in fig. 5, 

 as in all the many specimens now before me the base is narrower and more 



1 The oldest published name for this species is S. angustifolia Al. Br., 1837, but this name 

 was preoccupied by the living species. This fact was apparently recognized by Braun, as he sub- 

 sequently changed it to S. angusta, which is here adopted.— A. H. 



