188 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



this continent; none has been found until now in California and along the 

 North Pacific coast. Their range is especially in the whole area between the 

 great lakes and the gulf shores, except for U. crassifoUa, Nutt., which is not 

 known north of Arkansas, and TJ.Jloridana, Chap., limited to Florida. 



Considering its geological records, the genus seems of recent origin in 

 this country. The only species described here is from the Upper Miocene 

 of South Park. Three others are known from the Chalk Bluffs or Pliocene 

 of California; but in the Lower Lignitic, even in that of Carbon, no leaves 

 of Ulrnus have been found until now. One species, however, is described 

 by Heer, from the Miocene of Alaska ( U. plurinervia, Ung ), where it is repre- 

 sented by a single leaf, and another has been found in Oregon. None is 

 recorded from Greenland. Per contra, in Europe, the genus has a number 

 of representatives already in the Lower Eocene; three are described by 

 Saporta, from Suzanne, and twenty-two other species are recorded in Schim- 

 per's Pal. V^get, mostly from the Paleocene and the Lower Miocene forma- 

 tions. From all these representatives of old, the present distribution of the 

 genus upon the old continent seems normal. It does not appear to be the 

 same in North America, for while we find in the Phocene of California three 

 species of Elms, none has been left there in its present flora, and all the 

 American species are now, as remarked above, distributed on the eastern 

 slope. This fact represents only an apparent anomaly; the existence of the 

 Elms in California at the Pliocene epoch proving a persistence over the 

 whole continent of some types locally and more recently destroyed by glacial 

 agency. 



Uliniis tcnuinervis, Lesqz 

 Plate XXVI, Figs. 1-3. . 



Ulmus ienuinervis, Lesqx., Annual Report, IS?.*?, p. 412. 



Leaves small, thin, short-petioled, either round and equal, or cordate and inequilateral at the base, 

 lanceolate, gradually acuraiuato; borders unequally serrate ; lateral veins thin, more or less flexuous, 

 and curved in passing np to the borders. 



The leaves of this species are comparatively small, averaging six centi- 

 meters in length and less than three centimeters in width. Their nervation 

 is thinner, and the direction of the lateral veins less straight or more curved 

 than in any other species of this genus. By the great unequality of some of 

 its leaves and their doubly serrate borders, it is related to U. Braunii, Heer, 

 a very common species of the Miocene, whose leaves are also small. But in 

 the European form these are comparatively broader, most generally unequal 



