109 
Planer a nervosa Newberry 
Plate XVII, figure 5 
Planera nervosa Newberry, U.S. Nat. Mus. Proc., vol. 5, p. 508, 1883; U.S. 
Geol. Surv., Mon. 35, p. 82, PI. 47, figs. 2, 3, 1898. 
XJlmus plurinervia Heer (not Unger), FI. Foss. Arct., Bd. 5, p. 39, PI. 10, 
figs. 3, 4, 1878; Bd. 7, p. 93, PI. 89, fig. 8, 1883. 
The type of this species was described from the Green River Eocene 
of Wyoming. It is probably an Ulmus, at least I do not believe that the 
leaves of Ulmus and Planera can be differentiated, although the present 
species has the form of leaf that is commonly referred to the genus Planera. 
There are somewhat larger leaves in the collection from Kitsilano than the 
one figured. The species appears to represent a descendant from the Fort 
Union species Ulmus wardi Knowlton and Cockerell, which Ward origin- 
ally named Ulmus planeroides. It is also identical with the leaves from 
western Greenland, Sakhalin island, and the Kenai formation of Alaska 
that Heer referred to the European Miocene Ulmus plurinervia of Unger. 
Order, Ranales 
Family, trochodendraceae 
Genus, Trochodendroides Berry 
Trochodendr aides arctica (Heer) Berry 
Plate XIII, figures 1-4 
Populus arctica Heer, FI. Foss. Arct., Bd. 1, pp. 100, 137, PI. 4, figs. 6a, 7, 
PI. 5, PI. 6, figs. 5, 6, PI. 8, figs. 5, 6, Pl. 17, fig. 5, PI. 21, figs. 14, 
15a, 1868. 1 
It has long been a matter for comment that many of the fossil leaves 
referred to Populus are unlike the existing species of that genus, and 
Saporta once proposed to refer some of them to the family Menispermaceae. 
Leaves of the type referred to are exceedingly common in the collection 
from Kitsilano, and these range in size from small, elongate, cordate leaves 
to larger ovate, orbicular, and cordate leaves. One might differentiate 
several nominal species if one followed the prevailing fashion of species 
making, but after a careful study I am convinced that they all represent a 
single botanical species. A similar criticism could be made, for example, 
of the numerous species of so-called Populus figured by Ward from the 
Fort Union deposits of the United States. 
After a thorough comparison with recent material, I believe that the 
forms under discussion should be referred to the family Trochodendraceae, 
and I have accordingly transferred them to the form-genus Trochoden- 
droides. If the reader will compare the accompanying figures with the 
leaves of the existing genera Tetracentron or Cercidophyllum he will find 
that they can be exactly matched. The smaller fossil leaves are identical 
with the seedling leaves of Cercidophyllum, and the larger are identical 
with the mature leaves, and this identity does not obtain when these leaves 
are compared with those of the genus Populus. I believe that the majority 
of these common types in the Eocene of high latitudes represent the former 
existing type, now restricted to eastern Asia. 
1 As the forms referred, to this species and supposed related species are so greatly in need of critical revision, as. 
in fact, are most of the Eocene specieB referred to Populus, no additional citations are given. 
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