258 UNITED STATES GEOLOGICAL SURVEY— TEETIARY FLORA. 



until now are Eocene. The primary netting is, as described in the diagnosis 

 of the genus, in quadrate or trapeziform meshes; the ultimate areolation, as 

 seen in fig. 12, consists in small irregularly quadrate cells. Two of the leaves 

 (figs. 10 and 12) are nearly entire; in fig. 12, however, the lateral nerves and 

 their branches are extended to the borders, forcing them out here and there, 

 and proving a disposition to the same kind of divisions as in fig. 11. The 

 same character of a more or less distinct denticulation is seen also in the 

 species of the Sezanne Flora {ioc. cit.). 



Habitat. — Black Buttes, Wyoming; not common. 



Grewiopsis tenuifolia, sp. nov. 



Plate XL, Fig. 14. 



Leaves membranaceous, rounded or cordate, taper-pointed, subiialmately nerved ; borders irregu- 

 larly dentate; lateral nerves mostly craspedodrome or entering the teeth by strong nervilles. 



This species, though rejiresented by a single fragment, seems ditferent 

 from the former, to which it was originally united. The tripalmate nerva- 

 tion is more distinctly marked by the prolongation of the lower lateral veins 

 into more prominent teeth, giving to the leaf a slightly trilobate form. The 

 secondary nerves are more distant, less numerous, three or four pairs only, 

 while in the former species the number is generally double. The consist- 

 ence of the leaf is also different. It is rather thin, membranaceous, of a 

 reddish color, and all the veins are thin, though quite distinct to the eyes, as 

 well as the veinlets, which are of the same character as in both the former 

 and the following species. Its relation is with G. anisomera. Sap. (Fl. Foss. 

 de S^z., p. 409, pi. xiii, figs. 8, 9), whose nervation is subpalmatc and the 

 leaves of much larger size than ours, and more still with G. sidcefolia, Sap., as 

 represented in the text (p. 407) of the same work, a figure which exemplifies 

 the nervation, nearly exactly as it is in our species. But the nerves are 

 thick in the European species, and the fragment indicates a larger leaf. The 

 author remarks, however, that Ihe nerves are prominent underneath; but 

 that in the upper surface they are merely defined or obsolete. But for the 

 larger size of the leaves, therefore, the characters are alike. 



Habitat. — Black Buttes, Wyoming; with the former. 



