708 KwNnowtton: Fossitt PLANTS FROM PORCUPINE BUTTE 
right angle to the midrib, slightly arching upward and provided on 
the lower side with some 6 or 8 secondary branches, which also 
apparently fork and end in the teeth; nervilles numerous, strong, 
mostly percurrent and unbroken ; finer nervation producing quad- 
rangular areas. 
The example figured was the only specimen contained in the 
collection ; unfortunately it is not perfectly preserved, especially 
in its margin. It appears to have been very broadly cordate-ovate 
or almost orbicular. As now preserved it is 11 cm. in length and 
about 10 cm. in width. From the configuration it seems hardly 
probable that it was more than 1 or 2 cm. longer or 1 cm. wider 
when living. The base is distinctly cordate, with well-rounded 
lobes. The margin, as already stated, is not well preserved, but 
from the manner in which the veins fork it was probably toothed 
throughout, with the veins ending in these teeth. The nervation 
is well shown in the figure. aS) 
On account of lack of knowledge regarding the margin it is 
impossible to compare this leaf closely with other species. At 
first sight it seems to be identical with Vzurnum antiquum (Newb.) 
Hollick,* which was called V. tilioides by Ward,+ but this species 
is not strictly palmately ribbed, although approaching it in some 
specimens. The most important point of difference is in the sec- 
ondaries, these being distinctly dichotomous in V. antiguum, and 
_ branching on the lower side in the leaf under consideration. 
3 It may be compared with Zilia populifolia Lesq.,t from Floris- 
sant, Colorado, this species being of about the same size. It has 
the margins deeply and regularly serrate, but appears to differ 
essentially in nervation. It is 5-ribbed from the base, as in ours, 
but the midrib is perfectly straight, with more numerous thin, 
_ Straight secondary branches, and the upper pair of ribs do not arch 
upward but pass straight to the margin on the same angle that 
they. arise. The secondary branches are also thinner. They 
__ fork, however, sending branches into the teeth, as presumably the 
present one does. 
Among living species this form seems to approach most closely 
to 7. Americana, which agrees well in size and nervation. The 
* Later Extinct Floras, 128. /. 33. f. 1, 2. 
a t Types of the Laramie Flora, 107. pl. 50-52. f. 1, 2. 
ae tCret. & Tert. Fl., 179. pl. 34. f. 8 
