INVESTIGATION OF TEMPERATURE CHANGES. 245 



epoch, when wide surfaces of land were slowly emerging from the sea. The 

 character of the climate, as to temperature, is indicated by the remark that 

 the vegetation was somewhat similar in its aspect to that of the swamps now 

 existing along the Gulf shores of the South. 



The flora of the second of the four groups mentioned above is largely iden- 

 tical with that of the Lower Lignitic. It differs from it, however, in that it 

 contains, so far as yet known, no leaves of Sabal or other j^alms, although 

 some fruits have been found, which have been referred to that family. This 

 group has not as yet been sufficiently studied to positively fix its position or 

 character. 



The flora of the third group is a peculiar one, and decidedly mixed in its 

 character. It is especially known from the fossil plants found in abundance 

 in the shales which overlie the beds of lignite at Carbon. The general char- 

 acter of these plants is decidedly Miocene, and they are closely related to 

 those of the same division of the Tertiary in Europe, and also to those of the 

 Miocene Arctic flora of Greenland and Spitzbergen, of which notice will be 

 taken farther on. Mr. Lesquereux thus characterizes this very peculiar and 

 interesting flora : '' Of the fifty-six species which represent it, eighteen are 

 identical with forms of the European Miocene, and thirteen with those of the 

 Arctic flora described from Alaska, Greenland and Spitzbergen. It has still, 

 however, a few species that may be considered remnants of the Lower Lig- 

 nitic, and are not present in the Arctic Miocene : among others, a Cinnamommn, 

 a Flcus, a Sinilax, and a Rhamnus ; the two last represented by large leaves. 

 It unites therefore in its characters, Miocene Arctic types with Miocene types 

 of Middle Europe, and a few of those of the Lower American Lignitic, con- 

 sidered as subtropical. This reunion of types at the same point indicates the 

 wide extent of the thermal zones during the Miocene period, as well as the 

 concordance of the floras over wide areas, even under distant degrees of 

 latitude."* 



The fourth group is much less important, so far as yet known, than the 

 third. The flora is related to that of the European Miocene in but a slight 

 degree, while it is more closely allied to that existing in North America at 

 the present time. " From the preponderance of Conifers and shrubs, the cli- 

 mate of this epoch appears to have been somewhat colder than at the former 

 period." 



As Mr. Lesquereux remarks, a wide field is opened for discovery and 



• 1. c, pp. 12, 13. 



