150 DESCRIPTION OF SPECIES. 



As represented upon the plates, the leaves would seem to be referable 

 to two different species. The fragments, however, are so well mixed 

 together that sometimes one leaf appears acutely dentate on one side and 

 obtusely so on the other. 



Hah. — Alkali Station, Wyoming. Professor iScudder. 



M y r i c a i a s i g it i s , Lesqs. 



" U. S. Geol. Rep.," vii, p. 135, pi. Ixv, figs. 7, 8. 



This species has a degree of relationship to the preceding. 



BETULACEJ^. 



BETULA, Linn. 



" U. S. Geol. Rep.," vii, p. 137. 



Betula Florissanti , sp. nov. 



Plate XXVII, Fig. 11. 



Leaves small, lanceolate-acuminate, nueqnilateral at the cnneate base, borders 

 donbly serrate; medial nerve thin; secondary nerves generally opposite, cnrved in 

 pa.ssing to the borders, branching, entering the teeth like the branches and united by 

 nei'villes. 



The leaf, 6 J centimeters long, li broad, appears unequilateral at the 

 narrowed base. The primary and secondary teeth are small, acute, and 

 turned upward. 



Hah. — Florissant. Princeton Museum. 



Betula truncata, sp. nov. 

 Plate XXVIII, Figs. 7, 8. 



Leaves short and short-petioled, ovate-lanceolate, truncate or rounded at base, 

 simply dentate; lateral veins at a broad angle of divergence, numerous, parallel, the 

 lower opposite. 



The leaves, 3 to 4 centimeters long, 2 centimeters broad, equally dentate 

 from near the base, have the secondary nerves at an angle of divergence 

 of 60°, generally branching. The relation of this species is to Betula 

 crenata, Ung., " Schoss. Fl.," p. 11, pi. iii, figs. 7, 8. The lateral nerves are 

 more open, more numerous, and less curved in the American species. 



iTaJ.— Florissant. U. S. Geol. Expl. Dr. F. V. Hayden. 



