236 THE FLOIIA OF THE DAKOTA GROUP. 



gravels of California, from specimens doubtfully referable to the Upper 

 Miocene of that locality. It is represented by numerous specimens in the 

 collection of tlie U. S. National Museum from John Day Valley, Oregon. 

 Heer has not found remains of Fagus in the schists of Atane nor in those 

 of Patoot, nor have any been observed in the Laramie Group. The distri- 

 bution of the beech, judging from its fossil leaves, is remarkable. That 

 the genus was already present in the middle Cenomanian of North America 

 is proved, not only by the leaves of two species described from the Dakota 

 Group, leaves Avhich are positively identified by the peculiar nervation 

 whicli characterize those of the genus, but also by a fruit figured by 

 Dawson from the Milk River series of Canada, and also by a species 

 described by Ettingshausen from the Cenomanian of Niederschoena, F. 

 prisca, the leaves of which have the same characteristic nervation as those 

 of the Dakota Group. In Europe, as in Nortli America, no traces of leaves 

 of Fagus are recorded between the Cenomanian and the middle Tertiary. 

 From North America one species has been recorded from the Green River 

 Group and five from the Miocene. The species in more recent floras grad- 

 uallv become more closely allied to the common American beech, until Ave 

 find in the Pliocene or Upper Miocene of the amiferous gravel dejiosits of 

 California the leaves of F. Feronire Ung., and of F. pseii(h-ferrii(jinea Lesq., 

 which scarcely differ from those of the living, indigeiious F. femif/hiea Ait. 

 Of the Salicinea;, the genus Salix (Avillow) is, as far as known now, 

 represented in the flora of the Dakota Group by numerous leaves, some 

 of them with obsolete nervation, whose determination is not positive; some 

 others, like S. nervUlosa Heer, S. deleta Lesq., whose relation to species of the 

 present flora is not clear ; and by others still, like iS'. pi-otccefoJta, as figured in 

 Lesq., Cret. and Tert. FL, PI. i. Figs. 14-16, distinctly characterized as leaves 

 of Salix by tlieir form and nervation, and still further }iya finely preserved 

 fruiting catkin, described and figured in this memoir (PI. VIII, Fig. G). 

 Therefore, the presence of the genus in the Cenomanian of North America 

 can not be disputed. As in the beech, the Cretaceous origin of the willow 

 is confirmed by the presence of one species in the flora of Quedlinburg 

 and one in that of the Quader of Germany. It is, however, reniarkidde 

 thiit no species of Salix has been recogiiized by Heer in schists of Atane 

 and none in the Senonian of Patoot. One only is mentioned liy Daw- 

 son, from the Upper Cretaceous of Vancouver Island. Higher up in the 

 measures, one species is recorded in the Laramie flora, viz, Salix Integra, 

 which is common in the European Miocene, and is also found at Black 



