THE FLORA OF THE SAINT EUGENE SILTS 



397 



deposits of approximately equivalent age, in the so-called "bone 

 caves" of Tennessee and Pennsylvania. It is evident that spe- 

 cies of hickory, closely allied to or specifically identical with the 

 existing pignut and shell-bark, were prominent elements in the 

 Pleistocene flora of North America. 



Order FAGALES 



Family Betulaceae 



Genus Betula Tjinnaeus 

 Betula ulmoides n. sp. 



PlATE 31, FIGURE 1; PLATE 32, FIGURE 1 



"Uhnus n. sp. Hollick, Summary Rept. (loc. cit.), p. 134. 



Specimens represented by basal parts of leaves that resemble 

 those of certain of our existing birches, such as the rounded or 

 cordate forms of Betula cordifolia Kegel, B. lenta Linnaeus, B. 

 lutea Michaux f., etc. 



The leaves vary in size, with rounded-truncate or subcordate, 

 and somewhat oblique or unsymmetrical bases suggestive of the 

 genus JJhmis, and finely dentate margins. 



A fragment originally identified as an Uhnus {loc. cit.) is 

 represented by figure 1, on piate 31 ; but it appears to be more 

 satisfactorily comparable with the genus Betula, and I have ven- 

 tured to include it in that genus together with the smaller speci- 

 men represented by figi^e 1, on plate 32. Satisfactory com- 

 parisons, or adequate specific description is impossible, in the 

 absence of any knowledge in regard to the shape and the mar- 

 ginal characters of the upper part of the leaves. For purposes 

 of comparison, however, I have introduced (plate 44, figure 1) 

 a figure of a typical average leaf of Betula leiita, the base of 

 which is closely similar to the basilar parts of our specimens. 

 Many individual leaves of B. lutea, however, with more conspicu- 

 ously oblique bases, might also be selected for comparison, and 

 it would be difficult to decide to w^hich of these two species our 

 specimens appear to bear the closest resemblance. 



