04: Later Extinct Floras of North Ameri 



Formation and Locality. Ferruginous shale. Banks of 

 Yellowstoue River. (Dr.Hayden.) 



Populus cuneata. (n. sp.) 



Leaves small. ol>< »\ :ii r, somewhat wedge-shaped at the base, ob- 

 tusely pointed at the summit, coarsely, ob1 usely, and irregularly den- 

 tate on the margins; three-veined, basilar nerves given off at an 

 acute angle, terminating above the middle of the margin: 

 mdary nerves few-forked, and often inosculating. 



This species is represented by numerous specimens in the 

 collection made by Dr. Sayden on the Yellowstone. It will 

 be seen to be distinctly separable from any of the species pub- 

 lished with it, and the same may be said in regard to those pub- 

 lished elsewhere. In general form it bears some resemblance 

 to P. attenuata, Al. Braun (Flor. Tert. Helvet. 2. S. 15. Taf. 

 lvii. and lviii.), also to some forms of P. mutabilis II.; hut 

 the nervation is less crowded than in those species, and both 

 are acuminate-pointed. 



Formation and Locality. Lignite Tertiary beds. Banks 

 of Yellowstone River. (Dr. Hay den.) 



9'oihiIii*. genet rix. (>>. sp.) 



Leaves large, cordate in form, acuminate; margins serrate, with 

 rather small appressed teeth; three-nerved; nervation sparse but 

 strong; midrib straight, with few small branches; basilar nerves 

 very strong; given off a1 an acute angle, much branched at the 

 summit, reaching nearly to the margin far above the middle; 

 from each of the basilar-lateral nerves spring 5-6 exterior branches, 

 the lower cues very strong and branched, the upper slender and 



simple. 



In general aspeel this leaf is very similar to that of tho liv- 

 ing P. baleamifera, and apparently differs from it only in its 

 nervation. It is more decidedly three nerved than those of 

 any of the living group which it may he supposed to represent 

 — /'. balsamifera, 1*. candicans, /'. monilifera, etc., — yet one 

 may occasionally find a leaf of either of these species which in 

 this re-p<ri approaches the fossil before us. The dentation of 

 the margin ie essentially that of P. bafoamifera, and it can 



