AGE OF THE LIGNITIU DETERMINED BY ITS FLOEA. 333 



the first and tlie tliinl division. The same may be said of the climalic 

 circumstances evidenced by the plants. 



The tliird group, that of Carbon, has, by its thirty-seven species, an 

 evident Middle Miocene facies indicated by the relation of its plants to 

 the Miocene flora of Alaska, Greenland, Spitzbergen, and of Europe also. It 

 is clearly defined in the few localities which are referred to it, either con- 

 sidered in its proper plants, or separately from its affinities with the floras of 

 the other groups. It has, at Carbon, seven species; found also at Washakie: 

 Acorus hranchystnchys of the Spitzbergen flora; Corylus MacQuarrii of Alaska 

 and Greenland; Populus decipiens, same type as Paliurus Colombl of the 

 Miocene of Alaska; Platamis aceroules, P. Guillehnce, both common in the 

 Middle and the Upper Miocene of Europe (Oeningen), and also of Green- 

 land and Spitzbergen, with Paliurus Colomhi and Carpites cocculoides. Of 

 the two species of Fort Fetterman, Carbon has Taxodiuin distichum mio- 

 cenkum, whose relation of age is indicated by its name, and, with Rock 

 Creek, Populus subrotiDidata, closely allied to P. atlenuata of Oeningen. 

 This Populus is also in the Union group. Of species discovered at one 

 locality only, we have at Carbon, Quercus platania, described by Heer, from 

 specimens of Greenland and Spitzbergen; Zizyphiis Meekii and Z. hyperboreus, 

 two species closely allied, even perhaps identical, the last of which is in the 

 Greenland Miocene; Asimiua Eocenica, com\)i\.vQ\Ac io the YWmg A. triloba; 

 and two others, whose affinity is not yet clearly recognized, Ficus obovata 

 and Coccoloba Icenigata, this last one, however, compared to a species of the 

 present flora. Rock Creek has for itself Quercus Valdensis, a Miocene species 

 of Europe, Q. Haydenii, Q. acrodon, and Populus Icevigufa, representing 

 Miocene type, though not identified with any other species. From Washakie, 

 we have Populus latior, a most common and variable species of the Upper 

 Miocene of Europe, especially of the Oeningen flora, found also at Alaska; 

 and from Fort Fetterman Betula Vogdesii, a Miocene type. Four species 

 more are ascribed to this group from an isolated locality eight miles south- 

 east of Green River Station, cousiflered by its geological station as referable 

 to the Washakie group. They are Musophyllum complicatum, Lomafia? 

 microphylla, Sapindus vblusifolius, and Alnus Kefersteinii. This last is 

 common in the Upper Miocene of Europe, and has been also described from 

 Alaska, Greenland, and Iceland. Sapindus obtusifolius has its affinity with a 

 species of the Union group, S. mcmbranacais ; the two others are allied to 



