61 



whose relation cannot be positively affirmed if the seeds or other essential 

 characteristic organs are not discovered. The number of leaves, however, 

 which have to be referred to the same order of the vegetable scale tends to 

 confirm the relation of these leaves as it is indicated. The leaves referred 

 to the Proteinece or to an Australian type are mostly, if not all, without 

 nervation, and therefore of a far more doubtful relation. With us, at least, 

 the Eocene formation has scarcely any well recognized species of willows ; 

 none as yet whose characters are as evident as in the Cretaceous leaves. 

 They become, however, more predominant in the Carbon and Evanston 

 groups of the Tertiary, and especially in the Pliocene. 



Habitat. — Near Decatur, Hayden. Not found elsewhere; ten specimens. 



Amentacece. 

 Betula bkatriciana, Lesqx., PI. v, Fig. 5, PI. xxx, Fig. 4. 



Leaves small, rhombic-obovate in outline, cuneiform from tho middle downward to the petiole, 

 rapidly tapering from above the middle to a point, unequally simply toothed in its upper part, uudulato 

 entire to the base; nervation pinnate, craspedodrome. 



Betula beatriciana, Lesqx., American Journal of Science and Arts, loc. cit., 

 p. 95. 



The species was at first represented by one leaf in three fragmentary 

 specimens. Leaf 6 centimeters long and 3 centimeters broad, rhomboidal, 

 cuneiform from the middle to the base, marked above by a small pointed 

 lobe or tooth on each side, and hence contracted upwards and tapering to a 

 slightly obtuse point ; irregularly and simply toothed or undulate lobed in 

 the upper part ; secondary veins irregularly distant, but parallel, at an acute 

 angle of divergence (40°), six to seven pairs, branching near the point, nervilles 

 strong, more or less continuous and at a right angle to the veins. Another 

 leaf discovered lately has the same essential characters as the other, being, 

 however, smaller with equally distant closer secondary veins. The lowest 

 veins in this leaf also are thinner, marginal or parallel to the borders, and join 

 the middle nerve above its' base. 



This species is, by the form of its leaves and its nervation, comparable to 

 some of the numerous varieties of Betula nigra, L. The only evident differ- 

 ence is in the simply dentate border of the fossil leaves, which are doubly 

 serrate in the present species. In the Phyllites du Nebraska, Professor Heer 

 has described under the name of Betulites dentkulata, p. 15, PI. iv, Figs. 5 and 



