834 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



Euri)i)(>;iii Miocene types. Tlie ^Miocene i'acies of the Carhoii groiij) is not 

 contradicted by the few species which it has in coniiiion with those of the 

 other divisions of the Lignitic Tertiary ; for to tlie fir.^t group it is allied 

 only l)y IM'nnenltes major, a marine plant whose wide distribution has 

 been remarked, Ficus tiliaJhUa, Cinnamanium aj/inc, whose relation is with 

 Miocene plants of Europe, and Fiats nncala, of unknown affinity. No 

 Eocene type is seen in this third group. It has, in common with tlie Evans- 

 ton or second group, Popxlus urctica of the Miocene of Greenland, besides 

 Ficus tilia-folia, PojJiilus subrofundata, Alniis Kefersteinii, species already 

 named as ]\[iocene. The only species of unknown affinity described from 

 the second and the third group is Betula Stevensoni. 



With the fourth group, the relation presents the same degree of analogy 

 b}' Miocene types: Pojmlus arcticn, Ahms Kefersteiiiii, Acorus hranchysfachyc, 

 already considered; Juglans denticulata of the Baltic and Greenland Mio- 

 cene; Acer bilohatum. a predominant species of the Miocene of Europe, 

 which has not yet been recognized iii the Arctic regions; Eqmsetum 

 Hiiydenii and Cissus Parroticefolia, Miocene types also, the last, however, 

 not positively identitied with any species of that epoch. Hence we have, 

 in this Carbon group, not only the relation of age indicated by most of the 

 plants described from it, but also that of climate, proved by the affinity of 

 the largest number of its species with those of Greenland, Spitzbergen, and 

 Alaska. The plants evidence a climate like that of the middle zone of 

 the United States at our epoch; as from Ohio to North Alabama. 



I have separated the Green River or i()urth group in two parts on 

 account of the indefinite relation of the species of each of them, and there- 

 fore of the peculiar facies of their llora. I am, moreover, uncertain in regard 

 to the exact locality of a number of specimens, which were sent without 

 labels, and which I refer to the Lower Green River group by mere affinity 

 of types, specimens which represent especially Ficus arenacea in its various 

 forms, and Cinnamommn affine. 



The position of the Green River group as fixed by stratigrajihy is above 

 the Washakie or Lignite productive group. Its comi)oun(ls are peculiar, 

 mostly deposits of shallow fresh-water lakes, containing a profusion of iish 

 remains, and rich in bitumen, resulting from animal decomposition, rather 

 than from the growth of l)oirgy plants; for until now, to my knowledge, 

 no bed of true Lignitic coal has been discovered in this formation. The 



