148 



LOWER EOCENE FLORAS OF SOUTHEASTERN NORTH AMERICA. 



neoplanicostata, Ficus occidentalis, Ficus 

 artocarpoides, Osmanthus pedatus, Euonymiis 

 splendens, Leguminosites arachioides, Comhre- 

 tum ovalis, Magnolia angust [folia, Magnolia 

 leei, Cinnamomiim mississippiensis, Nectandra 

 lancifolia, Zizijphus meigsii, ApocynoplvjUum 

 wilcoxensis , Terminalia lesleyana, and Tcrnii- 

 nalia hilgardiana. Sixteen of these species are 

 peculiar to the two formations. 



In addition to the species common to both 

 formations a number of closely related forms 

 are found in each formation, the distinctness 

 of some of them being a matter of personal 

 opinion. The following Wilcox species are 

 represented by closely allied forms in the 

 Raton formation: Aneimia eocenica, Aspleniitm 

 hurley ensis, Pteris psevxlopinnseformis, Chamie- 

 dorea danai, Canna eocenica, DryopJiylhim 

 puryearensis, Aiiocarpus wilcoxlana, Cinna- 

 momura oblongatum. Cassia glenni, Sophora 

 henryensis, and Sapindus eoligniticus. 



This is an imposing array of identical or 

 closely related forms and indicates that the 

 two floras can not differ very materially in age; 

 that is, that one can not be Eocene and the 

 other Cretaceous. The Wilcox differs from the 

 Raton flora in the large number of Leguminosae 

 and Lauracese, and in the presence of many 

 genera whose representatives still live in the 

 tropical and subtropical regions of America. 

 The presence of 2 Laramie species in the Raton 

 and the fact that the commonest and not the 

 most significant forms usually occur in re- 

 mote areas, leads me to the conclusion that the 

 Wilcox flora is somewhat younger tlian the 

 Raton flora to which it bears the same rela- 

 tion that it does to the Midway ( ?) flora. This 

 conclusion is also influenced by the strati- 

 graphic relations in the embayment area and 

 the result is that I consider the Midway as in 

 whole or in part sjmchronous with tlie Raton. 

 I have seen a large amount of the Raton ma- 

 terial in connection with my WQcox studies and 

 have also visited the area and feel entirely 

 justified in the conclusion that it is of Eocene 

 age and slightly older than the Wilcox. 



FLORA OF THE DENVER FORMATION. 



Although fossil plants won- discovered in tlie 

 Denver Basin by Le Conte in 1SG7, it was not 

 imtil 1896 that the Arapalioe and Denver 

 formations were shown to be so sirikingly dis- 

 tinct from tile Laramie in structural relations, 



stratigrapliy, and fossil content.' Although the 

 flora of the Denver formation is large, it has 

 never been adequately described, and the dif- 

 ficulty of disentangling the early records is so 

 great tliat no list has ever been published. The 

 published Denver species number 98, according 

 to Knowlton.- Large collections have been 

 made, and the real Denver flora is undoubtedly 

 much more extensive, for many new species 

 are discovered when a fliira receives mono- 

 graphic study. 



Tlie following Wilcox species are recorded 

 from the Denver: A.^pleniuin eolignitica, Pteris 

 pseudopennseformis, Taxodium duhium, Sahalites 

 grayamts, Juglans sclnmperi, Artocarpus lessigi- 

 ana, Artocarpus jmngens, Ficus occidentalis, 

 Ficus denveriana, Ficus pscwdopopulus, Ficus 

 planicosiata latifolia, Leguminosites aracliioides, 

 RJiamnns clehurni, Aralia notata, Chinamomum 

 affine, and Cornus studeri. Eight of these species 

 have not been found in the Raton formation. 



Tlie foUowing Wilcox species are repre- 

 sented by closely allied forms in the Denver 

 flora: Ficus monodon, Ficus harrisiana, Ficus 

 planicostata maxima, Cinnamomum mississip- 

 piensis, Persea longipetiolatum, and Rhamnus 

 coushatta. 



According to Knowlton, nearly half the de- 

 scribed Denver species occur in the Raton flora, 

 and he is emphatically of tlie opinion that the 

 two floras are nearly if not exactly synchronous. 

 The Denver flora differs from that of the Wdcox 

 in the indivichial abundance and specific dif- 

 ferentiation of Quercus, Platanus, and Populus, 

 in the large number of ferns, and in the presence 

 of a Ginkgo. The families Aceraceae, Capri- 

 foliacese, and Vitaceae, wliich are present in the 

 Denver, are unknown in the Wilcox. 



What was said regarding the Raton flora is 

 equally true of the Denver flora, tliat though 

 it is somewhat older than the Wilcox flora its 

 similarities to that flora, as well as its facies as 

 a wliole, are sufficient to indicate its Eocene 



age. 



THE FORT UNION FLORA. 



The Fort Union formation has furnished a 

 very extensive flora, and although it was long 

 confused witli the Laramie both paleontologists 

 and geologists are now agreed that it is of 

 Eocene age. 



' Emmons, S. F., Cross, Whitman, and Eldridge, G. H., Geology of 

 the Denver Basin in Colorado: I'. S. (ieol. .'Survey Mon. 27, 1896. 

 2 Am. Jour. Soi., 4th scr., vol. 35, p. i2n. 1913. 



