knowlton.] DESCRIPTION OF SPECIES. 37 
This species has strong affinities with several well-known forms, as, 
for example, Populus nervosa Newb., from the Fort Union beds of 
Montana. The shape, size, dentation, and strong, coarse nervation are 
practically the same in both, P. nervosa differing, however, in being 
only three-nerved and in a tendency to be slightly three-lobed. Pop- 
ulus nebrascensis Newb., from the same beds, is apparently quite sim- 
ilar, but differs in having the first pair of basal nerves arching around 
and ascending to near the summit of the leaf. In the leaf under dis- 
cussion they appear to be lost long before reaching the margin. 
I take pleasure in naming this species in honor of Prof. Lester F. 
Ward, by whom it was collected. 
Habitat. — Point of Rocks, Wyoming, base of bluff northeast of sta- 
tion. Collected September 2, 3, 1883. 
Populus mutabilis ovalis? Heer. 
PL VII, fig. 3. 
Populus mutabilis ovalis Heer, Fl. Tert. Helv., Vol. II, p. 22, PI. LXI, figs. 1, 3, 6, 9; 
PI. LXIII, fig. 4; Lesquereux, Ann. Rept. U. S. Geol. and Geog. Surv. Terr., 1871, 
pp. 292, 401, 405; 1873, p. 397; Tert. Fl., p. 177, PI. XXIV, figs. 3, 4. 
The leaves referred by Heer to this form of this polymorphous species 
vary considerably, and as Lesquereux has said, " it is extremely hazard- 
ous to identify single leaves" with either of the forms. We are therefore 
permitted a certain degree of latitude in admitting forms under this 
name. They are all so connected by intermediate links that it may 
sometimes be difficult to decide to which form a particular specimen 
shall be relegated. The example here figured, from Point of Rocks, is 
with hesitation referred to this form. With more than one specimen in 
hand a more definite conclusion could undoubtedly be reached. 
Habitat. — Point of Rocks, Wyoming.? 
Populus sp. 
PL VII, fig. 5. 
As stated under Glyptostrobus ? sp. and under Phyllites sp., a speci- 
men was obtained from the coal mine on Duttou Creek which had three 
plants preserved on it — the one here figured and the specimens above 
referred to. As the piece of matrix in which these three forms was 
preserved is now lost, the figure is given simply to call attention to the 
fact that such a plant existed at that place, and to impress subsequent 
collectors with the desirability of obtaining further material. 
Habitat. — Coal mine on the north fork of Button Creek, near old stage 
road, Laramie Plains, Wyoming. Collected by Knowlton, Stanton, and 
Knight, July, 1896. 
