256 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



are considered by Schiinpor ns pertaining to the polymorphous Ficus tilicefolia, 

 cxeept that of fig. 1, pi. xxvii, of Uuger's Fl. v. Sotzka, whieh is precisely 

 the one to which this fragment is comparable The same plate of the author 

 has for comparison two leaves of the living Dombeya camhina, whose base is 

 deeply cordate, and the six-palmate nervation is of the same type as in the 

 fossil fragments of linger, to which ours is very similar. This fragment is 

 therefore, like those of the European author, of uncertain relation. The 

 petiole is thick, enlarged, and flattened at its top, where it divides in six equal 

 nerves, diverging star-like, joined by numerous strong nervilles, disconnected 

 and irregular in distance. It seems to have supported a large leaf 

 Habitat. — Golden, South Table Mountain, Colorado. 



TILIACE^. 



Two genera of this order are especially to be considered in regard to 

 their geological relation : Tilia and Grewia. The first, in the flora of the 

 present epoch, has its distribution limited to Europe and North America, and 

 nearly equally divided in both continents in the small number of its species, 

 four or five in Europe and three in the western slope of the United States. 

 Grewia has its numerous species in the equatorial and tropical regions of 

 Asia, especially Java, and of South Africa. A single species, even of doubtful 

 reference to this genus, is credited to this continent. New Granada. Hence, 

 considering this distribution, the presence of species of Grewia in the fossil 

 flora of North America would appear somewhat anomalous. • Until now, no 

 plant referable to this genus has been seen in the Lignitic formations of the 

 West, but there are some, whose relation is distinctly marked with leaves 

 described by Saporta under his new generic division Greioiopsis, which, 

 though its characters are not positively fixed in their relation, has its analogy 

 with the Tiliacece. of our time. Of Tilia^ I have not found any evident 

 representative in the Lignitic; but Dr. Newberry has described T. antiqua 

 from the Miocene of Fort Clarke, and Heer has one also, T. Alaskana, from 

 the same formation of Alaska. From the Tertiary of Europe, the authors 

 have described seven species of Tilia from leaves and two from seeds. 

 They have also six species referred to Greicia, and seven species of Apei- 

 hopsis, which apparently represent Apeiba, a genus of this order, which now 

 has half a dozen species, all limited to tropical America, Guiana, etc. 



