1890.] Origin of the Plane-Trees. 807 
ment from geology is erroneous. Let us look closely for a 
moment at the real geological and geographical distribution of 
the fossil species of Platanus, especially the American species. 
P. primeva Lx., is correctly referred to the Cretaceous, as it 
occurs only in the Dakota group of the United States. 
P. primeva heerit Jankó (P. heerü Lx.) is also primarily a Dakota 
group species, but occurs in the Mill Creek series of Canada and 
in the Atane beds of Greenland, both of which are considered 
equivalent to the Cenomanian of Europe, and therefore not 
greatly different in age from the Dakota group. But I found a 
form at Black Buttes in the typical Laramie which I referred to 
that species, admitting some differences. Professor Lesquereux, 
who was very tenacious of his views as to the Tertiary age of the 
Laramie, challenged, in a letter, my determination, and I am not 
quite certain that it is correct. It may be as near to another , 
Cretaceous species, P. newberryana, but it is not near to any 
Tertiary species. But P. heerü is not confined to the Cretaceous 
and Laramie if Gardner is right in reporting it from the Island of 
Mull at Ardtun, the Eocene age of that celebrated deposit being 
well established. On this point, however, there are doubts, as he 
only provisionally identifies the Platanites of Forbes with that 
species. j 
P. newberryana Heer, the other Cretaceous species, is, like the 
rest, a typical Dakota group form, and has not been found out- 
side the Cretaceous, nor, indeed, outside the Dakota group, except 
in the Patoot beds of Greenland, which, however, are consider- 
ably higher in the series, being referred by Heer to the Senonian. 
So much for the Cretaceous species. Next as to the alleged 
Eocene ones. 
P. rhomboidea Lx. is only known in two specimens from 
Golden, Colorado. An examination of the specimens themselves 
shows that they are from the so-called tufa beds of South Table 
Mountain, and therefore belong to the Denver formation of 
Emmons, which he places somewhat higher than the Laramie. 
It may therefore pass as Eocene. 
P. raynoldsii Newberry was originally described from the Fort 
Union group on the Missouri and Yellowstone Rivers, and I 
