DESCRIPTION OF SPECIES— SALIOINE^. 175 



§ II. — Trepida. 

 Populus l>'ng:cri,sp. nov. 

 Plate XXIV, Fig. 5. 

 Popniua heliadum, Ung., Lesqx., Annual Eeport, 1873, p. 397. 



Leaves subcoriaceous, long-petioled, bioadly ovate, obtuse; borders entire, slightly undulate; 

 secondary veins equidistant with the primary ones. 



This leaf, rather membranaceous than coriaceous, with a slender, appar- 

 ently long, petiole, has the form of Populus mutabilis repando-crenata, Heer, 

 as represented in Fl. Tert. Helv., pi. Ixii, fig. 1, and tlie nervation of P. balsa- 

 moides, Goepp., as in pi. Ix, fig 2, of tlie same work; the primary lateral 

 veins and the secondary ones being equidistant, and of the same thickness. 

 From the first of these species it differs by the nervation ; from the second, 

 by the entire borders of the leaves. From P. heliadum, Ung. (Fl. v. Sotzka, 

 p. 37, pi. XV, fig. 7), to which I referred it formerly, it differs equally by the 

 more numerous equidistant nerves, the less enlarged form of the leaf, and the 

 borders less distinctly undulate, linger describing them as undulate-dentate. 

 Other specimens may indicate a more positive relation. Except for its slender 

 long petiole and an apparently merely membranaceous or thin consistence, 

 this species should go to the section of the Coriaceous Poplars, and be per- 

 haps referred to P. monodon, represented in figs. 1 and 2 of the same plate. 



Habitat. — Golden, Colorado. 



§ III. — Balsamitce. 



Populns laevigata, Lesqx. 



Plate XXII, Fig. 9. 



Populus Icevigata, Lesqx., Annual Eeport, 1869, p. 195. 

 Populus (equalis, Schp.,* Pal. V^giSt., p. 693. 



Leaves large, cordate, acuminate, rounded to the base, dentate ; teeth acute, turned outside; midrib 

 much thicker than the lateral ones ; surface smooth or polished. 



This fine leaf, thirteen centimeters long, and eleven centimeters wide a 

 little below the middle, is so closely allied to Populus balsamoides, Goepp., 

 extensively distributed in the European Miocene, that it can only be separated 

 by the form of the teeth of the borders. The size of the leaf is equaled 

 by that of some of those published by the authors as pertaining to P. balsa- 

 moides; the middle nerve is in both species comparatively thick; the gen- 

 eral nervation and the areolation are the same. Many fragments seemingly 



• The name Populus wqualis mentioned was originally sent to Prof. Schimper with a photographed 

 figure of the specimen, and changed afterward without knowing that he had described the species. 



