AN EOCENE FLORA FROM TRANS-PECOS TEXAS. 



Although the geologic record is thus incom- 

 plete, it would seem to indicate a tropical ori- 

 gin for the tribe, possibly in late Upper Creta- 

 ceous time, a spread northward far into western 

 North America during the early Eocene, and 

 an invasion of southern Europe, possibly ex- 

 tending to tropical Africa, during the middle 

 Eocene or sUghtly later. An opinion as to 

 whether the tribe migrated to the Eastern 

 Hemisphere across the Tropics or in higher 

 latitudes is not warranted in the present state 

 of our knowledge. 



Geonomites has not yet been found in the 

 extensive Eocene floras from the shores of the 

 Mississippi embayment which I have described. 

 The fact that the bulk of these plants have 

 been collected from the old eastern shores of 

 this Eocene gulf may or may not be significant. 

 The absence of Geonomites in the Wilcox flora 

 rather lends support to the view that the basal 

 tuffs of the Barilla Mountains are somewhat 

 older than the Wilcox — that is, they are of 

 Midway age. I also conclude that the Raton 

 and Denver formations along the present 

 Rocky Mountain Front Range are hkewise 

 older than the Wilcox. 



Class DICOTYLEDONAE. 



Order JUGLANDALES. 



Family JTJGLANDACEAE. 



Genus JUGLANS Linne. 



Juglans rugosa Lesquereux. 



Juglans rugosa Lesquereux, Am. Jour. Sci., vol. 45, p. 206, 

 1868; The Tertiary flora: U. S. Geol. Survey Terr. 

 Kept., vol. 7, p. 286, pi. 83, figs. 4, 5; pi. 84, figs. 

 1-9; pi. 85, figs. 1, 2, 1878. (Not Lesquereux, 1888, 

 or Hollick, 1899.) 

 Knowlton, U. S. Geol. Survey Prof. Paper 101, p. 293, 

 pi. 112, fig. 4, 1918. 



This somewhat variable species had a wide 

 range durmg the Eocene in western North 

 America and has been recorded from Canada, 

 Montana, Wyoming, Yellowstone Park, Colo- 

 rado, California, Oregon, and New Mexico. It 

 is distinctly a lower Eocene type and is a 

 characteristic form in the floras of the Denver 

 and Raton formations. It was recorded from 

 the lower Eocene of the Mississippi embayment 

 region by both Lesquereux and Hollick, but 

 these occurrences do not represent this species, 

 which so far as known did not exist in that 

 region until later in the Eocene. Tlie species 



is represented by over a dozen specimens, 

 mostly fragmentary, in the basal tuffs of the 

 Barilla Momitains. 



Order BANALES. 



Family ANONACEAE. 



Genus ASIMINA Adanson. 



Asimina eocenica Lesquereux (?). 



Asimina eocenica Lesquereux, L. S. Geol. and Geog. 

 Survey Terr. Ann. Kept, for 1872, p. 387, 1873; 

 The Tertiary flora, p. 251, pi. 43, figs. 5-8, 1878. 

 Berry, U. S. Geol. Survey Prof. Paper 91, p. 14, 1916. 



Three or four not very perfect specimens in 

 the basal tuffs of the Barilla Mountains are 

 questionably referred to this species. It was 

 described by Lesquereux in 1878 in the follow- 

 ing terms: 



Leaves very entire, lanceolate, equally gradually taper- 

 ing downward to a short, thick petiole and upward to a 

 point; nervation pinnate, camptodrome. I have seen a 

 large number of specimens of these leaves, varying in size 

 from 8 to 15 centimeters long and from 2^ to 4 centimeters 

 broad in the middle, where they are widest, and there 

 oblong, gradually narrowing upward and downward. The 

 consistence of the leaves is somewhat thick but not coria- 

 ceous; the midrib thick, the lateral veins nimierous, 

 parallel, all under the same angle of divergence of 50°, 

 slightly curved in traversing the lamina, generally simple 

 or branching once toward the borders, which they follow 

 in a series of bows, formed by anastomoses with veinlets 

 or branches. The nervilles are distinctly marked, at least 

 upon some well-preserved specimens like the one of 

 figure 8; they are generally joined in the middle of the 

 areas by oblique veinlets, forming large equilateral meshes, 

 the ultimate areolation being indiscernible. These leaves 

 differ especially from our A. triloba by their oblong- 

 lanceolate shape, those of the living species being generally 

 enlarged upward and more distinctly oblong-obovate and 

 proportionally broader. The nervation compared in both 

 the small and the large leaves of the living species fully 

 agrees \vith that of these fossil leaves, the lateral veins 

 becoming closer and more distinctly marked in the small 

 leaves, as it is in figure 5. It is the same with the tertiary 

 intermediate nerves, which are scarcely, if ever, dis- 

 tinctly marked upon the small or middle-sized leaves of 

 the papaw, while they appear, if not numerous, at least 

 perfectly distinct, in the large ones. A fruit referable to 

 this genus is described in the Eocene [Wilcox] flora of the 

 Mississippi as Asimina leiocarpa Lesquereux. 



The species Asimina eocenica is common in 

 the Denver formation of Colorado and occurs 

 also at Carbon and Black Buttes, Wyo. It is 

 also present in the Midway ( ?) Eocene of 

 Texas. It has been recorded by Knowlton 

 from the Montana group, but this identifica- 

 tion I regard as mcorrect. It is probably 

 present in the Raton formation, being not 



