254 THE FLORA OF THE DAKOTA GROUP. 



ill tlie still iiiore recent formations referred to tlie Miocene ten species are 

 described, four of which are from leaves found in the auriferous gravel 

 deposits of California; this in a flora of which only fifty-four species are 

 known. Cari/a aiiflqna Newb., ascribed to the Laramie Group, has been 

 found in the Bad Lands and the Fort Union Group, with plants of Miocene 



The Jug-landese show a constant increase of their representatives in 

 the floras of the Mesozoic ages in passing from older to more recent forma- 

 tions. The present flora of North America has now fom* species of Juglans, 

 two on each slope, and seven species of Carya, all confined to the Atlantic 

 States. Tiie predominance of the Juglandeoe upon this continent is the 

 more remarkable in that, of the thirty species of Juglans still living, Europe 

 has only one species and this in cultivation, anil as far as known introduced 

 from Persia, Avhile thirty-four species have been described from leaves or 

 fruits from the European Miocene, with eighteen species of Carya and five 

 of Pterocarya. The original type of Juglans is represented in the Dakota 

 ( xroup by leaves with entire borders. No species with serrate leaves, like 

 those of Juglans and Carya of our present flora, have been observed before 

 the end of the Cretaceous. 



(^f the Rosacese we have in the Dakota Group well preserved leaves 

 of one species of Crataegus, one of Pyrus, and two of Prunus. The leaves 

 of Crataegus have distinct characters and are positively determined. That 

 of Cratfcgiis Lam'cmiatui (PI. XXXVIII, Fig. 1) has a very close relation to 

 C. antiqua Heer of the Tertiary of Greenland, and both species are of a 

 type evidently reproduced in the living C. totnentosa Linn., of the present 

 North American flora. The determination of Pijnis crefacea Newb., based 

 ujion the form of one leaf and that of Primus cretacea Lesq., determined 

 from two fruits, may be, however, questionable, tiiough I have found in the 

 Senonian of Wyoming (Princeton collection) leaves referable to two species 

 of Prunus, one of which is closely related to F. serrulata Heer of the 

 Sachalin Tert. Fl. From the same formation a number of leaves have 

 been referred to Photinia on account of their distinct affinity to those of the 

 living P. arhutifolia of California, and others, together with fine large stipules, 

 to Crataegus on account of the affinity of their characters to those of C. 

 japonica. Heer has not recognized an-\- kind of plants referable to the 

 Rosaceac in the schists of Atane, but has describetl two species of Crataegus 

 from the Senonian of Patoot. In more I'ecent formations, considered as 

 Tertiary, one species of Amelanchier is described by Dr. Newberry from 



