138 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



sixteen to twenty-five millimeters broad in the middle; their form is nearly 

 oval, more enlarged, and rounded at the base, which seems to pass down 

 abruptly from near the petiole as decurring to it; they are minutely apiculate 

 and serrulate. The species is related by the nervation to B.dentkulafa, Goepp., 

 (Schoss. Fl., p. 12, pi. iii, figs. 14, 15), a species considered by European 

 authors as identical with B. caudata, Goepp. 



Habitat. — Fort Fetterman, Indian Territory {Lieut. Vogdes). 



Betula gracilis?, Ludw. 



Plate XVII, Fig. 20. 



Betula gracilis, Ludw., Pateont., viii, p. 99, pi. xxsii, fig. 4. — Lesqx., Aniiual Keport, 1873, p. 398. 



Leaf small, ovate, obtusely pointed, distantly serrate; middle nerve thick; secondary veins mixed, 

 some of them passing up in a curve to the teeth, simple. 



The form of the leaf is ovate, apparently rounded at the base, which is 

 destroyed; the secondary nerves, simple and curved in passing up to the 

 borders, have the same character as in Ludwig's figure (loc. cit.), being, how- 

 ever, less distinctly camptodrome, and more generally running to the point 

 of the small distant obtuse teeth. The European species is already of doubt- 

 ful reference as remarked above, and therefore this fragment of a leaf is still 

 more uncertain in its determination. 



Habitat. — Golden, Colorado. 



Betula Ooeppcrti, Lesqz:. 



Plate XVII, Figs. 21-23. 



Betula caudatal, Goepp. — Lesqx., Annual Report, 1871, p. 293. 



Leaves large, ovate, subcordato or rounded at the base, lanceolate-acuminate ; borders irregularly 

 crenato-serrate ; secondary nerves half open, subcamptodrome, thin, joined by close nervilles in right 

 angle. 



These leaves are referable to Goeppert's species by their form, their size, 

 and their nervation; the acumen is also generally inclined on one side, as in 

 the European species. But, as remarked from a number of specimens, with 

 borders more distinctly preserved, they have the teeth of the borders of a 

 different character, not turned out and spinulose, but inclined upward and 

 rather obtuse, as seen in fig. 23 a, enlarged. The veins, whose angle of diver- 

 gence is 30° to 40°, are obsolete toward the borders, appearing either to 

 enter the points of the largest teeth, or to be effaced and lost in the areolation, 

 which is obsolete. As seen in fig. 21, the lower veins are opposite. 



Habitat . Evanston, Wyoming, where Dr. A. C. Peak collected the 

 first specimens. 



