176 UNITED STATES GEOLOGICAL SURVEY— TERTIAEY FLOKA. 



referable to P. balsamoides have been found in different parts of the North 

 American Lignitic formations, at Golden, Black Buttes especially; one also is 

 from Mount Diablo, California; but these fragments are all too insufficient for 

 positive identification; and the difference in their stations seems to contradict 

 an identity with the Miocene species. Good specimens of P. bakamoidca 

 have been, however, procured from the Miocene of Coral Hollow, California, 

 and have been figured for the Fossil Tertiary Flora of that State. Heer has 

 described it from specimens of Alaska. 



Habitat. — Rock Creek, Laramie Plains, Wyoming {Dr. F. V. Hayden). 



Populus Zaddacbi, Heer. 

 Plato XXII, Fig. 13. 



Popttlvs Zaddachi, Heer, Fl. Foss. Arct., i. p. 98, pi. vi, figs. 1-4 ; xv, fig. lb; ii, p. 468, pi. xliii, fig. 1.5; 

 xliv, fig. 6; Fl. Fo88. Al.isk., p. 26, pi. ii, fig. 5a; Spitz. Mioc. Fl., p. 55, pi. ii, fig. 13c; i, 

 fig. 1 ; xi, fig. 8 a ; Mioc. Bait. Fl., p. 30, pi. v, vi, figs. 1-7 ; xii, fig. 1 c— Lesqx., Annual Report, 

 1871, p. 292. 



Leaves ovate, obtuse, rounded or subcordate at the base, crenate, ptilmately five-nerved ; upper 

 primary lateral nerves at an acute angle of divergence, ascending to above tbe middle of the leaves. 



This species, very common in the Miocene of the Baltic, of Greenland, 

 and of Alaska, has, until now, few representatives in this country and none in 

 the Lower Lignitic. It is found with the following species in the Upper 

 Tertiary measures, especially abundant in the Pliocene of California. By 

 comparison, it will be seen that our leaf has exactly the characters of those 

 figured in Fl. Bait., pi. v, figs. 2 and 5, the lower lateral veins being effaced 

 and very short, and the base of the leaf being rounded in narrowing to the 

 petiole. The general nervation is also the same, the primary upper lateral 

 nerves being much thinner than the midrib, indeed, of the same size as the 

 secondary ones, which are at a comparatively great distance from the basilar 

 nerves and at a much more open angle of divergence. The teeth of the 

 borders are of the same form, obtuse or half-round, turned upward. The 

 size of the leaves of this species is very variable; ours measures six centi- 

 meters long and nearly five centimeters broad. Heer figures one from the 

 Baltic Miocene, sixteen centimeters long and twelve centimeters broad. 



Habitat. — Green River Station, Wyoming, above fish beds {Dr. F. V. 

 Hayden). 



