with Descriptions of JVt w Sp t cu s of 1 ,, l 



Of this neat species there are no complete specimens in I 

 collection; none of them showing the summit of the ti 

 Enough is, however, discernible in them to show that they 

 represent a species of Popvlus different from any other in the 

 collection; and from any before described. Of the Bp< 

 present growing on the North American continent, the leaves 

 of P. heterophyUa approach most nearly to these, bill the nerva- 

 tion of the leaves of that tree is never bo distinctly radiate. 



In the character of its marginal dentation this B] ru- 



bles P. mutahllls, var. crmata^ Eeer,*but is clearly distinguish- 

 ed from that by its cm-date base, and corresponding rad 

 venation. 



Formation and Locality. Miocene Tertiary strata, Bai 

 of Yellowstone River. (Dr. Harden.) 



l*o pul ii« nervosa (n. Bp.) 



Leaves rounded in outline, margins nearly entire, or Blightly ser- 

 rate at the base, sharply but not deeply toothed on the Bides, on the 

 summit strongly doubly serrate, with a tendency to become ti 

 lobed; nervation strongly marked an. I crowded; basal nerves 

 springing from the midrib above the margin, given off at an ai • 

 of 30° or more, reaching the margin above the middle, where 

 they terminate in the most prominent teetb or lobes; from tl 

 basilar nerves are given off five or six strong lateral n< rve*, which 

 arch upward and, more or les> forked, terminate in the marg 

 teeth; above the basilar nerves three or tour pairs of strong lab 

 nerves are given off from the midrib, which run parallel with the 

 basilar pair, and terminate, like them, in the compound u eth ol 

 upper margin. The lateral nerves are c< mnected by num< 

 secondary nerve-, which are generally simple and slightl) 

 sometimes broken, and anastomosing with each other. 'I 

 character gives a lattice-like appearance t'i the V 

 usual in the genus. 



The strong nervation of this species is one of i I 

 characters, and ha- suggested the name . L I!;. this and 



the double dentation of the superior mai 

 their aceriue form, these leav< y distinguishable from 



