no. 2074. STUDIES ON FOSSIL FLORA— BERRY. 303 



The proportion of still existing species and the occurrence of one of 

 the two fossil species, i. e., Salix viminalifolia, in the late Pleistocene 

 (Chowan formation) of North Carolina would seem to indicate that the 

 deposits of the Hickman and Columbus Bluffs are of late Pleistocene 

 age, but since the range of both existing and fossil plants in the 

 Pleistocene is so imperfectly known this is not demonstrated. Since a 

 majority of the forms recorded are prevailingly southern forms, and 

 several, as Vlmus alata, Planera aquatica, Cebatha Carolina, Xolisma 

 ligustrina, find their present northern limit near the latitude of Colum- 

 bus, it follows that the climate was not very different as regards rain- 

 fall and temperature from that of the present in western Kentucky. 

 This is also indicated by the fact that several of these species attain 

 their maximum development at the present time in the lower valley 

 of the Ohio. It is obvious that this flora is preglacial, intergiacial, or 

 postglacial in age, which is as definitely as it can be correlated until 

 more extensive data are available for comparison. 



Although I regard it as younger, there is a possibility that the 

 flora of the Hickman and Columbus Bluffs may be contemporaneous 

 with an extensive flora, as yet undescribed, from southern Alabama 

 and Mississippi, that I have considered to be of late Pliocene or early 

 Pleistocene, probably the former, age. In the absence of Pliocene 

 floras for comparison the question is rendered very complex. 



The question of exact age of late Tertiary and Quaternary floras is 

 still further complicated by the uncertainty as to when the Pliocene 

 ended and the Pleistocene began. Like the comparable question of 

 the boundary between the Pleistocene and the Recent, it is dependent 

 almost entirely upon latitude. Until the whole subject can be con- 

 sidered in a philosophical and comprehensive way and in the light of a 

 far greater array of facts than are at present available, any extended 

 discussion is futile. Certainly as the term is ordinarily understood 

 the flora of the Hickman and Columbus Bluffs is Pleistocene. 



Types.— Cat. Nos. 34964-34968, U.S.N.M. 



EXPLANATION OF PLATES. 



Plate 12. 



Fig. 1. Xolisma ligustrina (Linnaeus) Britton. 

 2. Ilex, species. 



3-5. Cebatha Carolina (Linnaeus) Britton. 

 6. Ulmus alata Michaux. 

 All from the early Pleistocene of Hickman, Ky. 



Plate 13 



Figs. 1-5. Teeoma preradicans, new species. 

 Early Pleistocene of Hickman, Ky. 



