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PoputitTes Lesq. Am. Jour. Sci. 46: 93. 1868. 
Founded by Lesquereux to include leaves from the Dakota 
Group which are apparently related to Populus but differing 
in their generally entire margin, cordate outline, and cras- 
pedodrome venation, the latter character apparently wanting 
in our species. Some of Lesquereux’s species have since been 
transferred to the genera Grewtopsis, Hamamelites, Ments- 
permites, and Cissztes, leaving seven Dakota species and one 
species from the Upper Cretaceous of Vancouver Island. 
The genus Populus, although containing the oldest known 
dicotyledon at Kome, besides ten Dakota species and two 
Potomac species according to Fontaine, is so essentially a later 
genus that I prefer to include our leaf in the related genus 
Popuiites, thus obviating too great definiteness of relation to 
the existing genus. 
Populus contains about twenty-five species in the existing 
flora, all of which are confined to the northern hemisphere. 
Some twelve of these inhabit North America. The fossil 
species are numerous. 
Populites tenuifolius sp. nov. Fl. 49. f. 7. 
A leaf exceeding 10 cm. in length and nearly 12 cm. in 
width: margin in the upper part apparently entire or perhaps 
a trifle undulate; about 4 cm. of the right lateral margin is 
preserved and seems to bis pen crenate, but the indica- 
tions are very faint and be to the wearing away o 
the material. The aa is ane preserved, but I judge it to 
thin, alternate, unbranched except the basal ones, oe 
the midrib at an angle of about 45° and curving up 
others, giving off numerous branches to the latero-basal 
portion of the leaf. ea ill-defined, angular. 
I have been at a loss to correctly determine this leaf; it 
bears considerable resemblance to some of Lesquereux’s 
species of Protophyllum, but inasmuch as the latter is a syn- 
* Lesq. Fl. Dak. Group, fl. g2. f 1. 
