228 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



are quite as closely related by the forms and the nervation of their leaves as 

 are those which have been described and figured here. 1 therefore consider 

 them as representing different species, though great may be the analogy of 

 their characters. 



ASCLEPIADINEiE. 

 OLEACE^. 



FRAXmUS, Toumef. 



The impari-pinnate leaves of this genus have ovate-lanceolate, generally 

 acute or accuminate, leaflets, entire or more or less regularly denticulate, with 

 a subcamptodrome nervation, the secondary nerves being joined to the denta'e 

 borders by nervilles from their bows, or directly entering them. 



The genus has a number of species distributed in Europe, Asia, and 

 especially the North American continent, to which forty-five of them are 

 ascribed in De Candolle's Pi-odromus. . But the number has been greatly 

 reduced by a more careful determination, especially of the fruits; for of the 

 thirty species described from the United States in that work, we find now 

 only six admitted in Gray's Flora. This number, still considerable, accords 

 with that of the fossil species known until now from this continent; for 

 two are described and figured here, one of them common to Europe, the 

 Baltic Flora, and Greenland; and two others are described only from speci- 

 mens received too late for illustration. One from Golden is typically allied 

 to the present F. Americana, by numerous leaves, which, either entire or 

 sparingly dentate, are stiil larger, and of the same shape and nervation; and 

 another, represented by a single leaf from the Upper Miocene of the Parks, 

 seems also distinctly referable to this genus. The European authors have 

 described seventeen species, all Miocene The species from Golden relates 

 the origin of Frarinvs to the Eocene. 



Fi'^xinns denticulata, Heer. 



Plate XL, Figs. 1,2. 



Fraximts denticulata, Heer, F). Foss. Arct., i, p. 118, pi. xvi, fig. 4 ; xlvii, fig. 2; Mioc. Bait. F)., p. 89, pi. 

 xii, fig. 27 ; xxiv, figs. 2B-27.— Lesqx., Annual Report, 1872, p. 407. 



Leaves oyong, obtusely pointed, graf-ually narrowed to the Bessile base. 



Our leaves are small, of the same size and form as 1hose described from 

 Greenland, Ihe secondary veins curving near the borders, with nervilles pass- 

 ing lo the teeth from the bows, as in fig. 4 of pi. xvi in Ihe Greenland Flora; 



