fc24 Wortman — Studies of Eocene Mammalia in the 



Bwamp-cypress (Taxodium distichum) now found living in 

 the Southern United States! There are also eleven pines, two 

 Libocedrus, two sequoias, with oaks, poplars, birches, planes, 

 Limes, a hazel, an ash, and a walnut; also water-lilies, pond- 

 weeds and an iris — altogether about a hundred species of 

 flowering plants. Even in Grinnell Land, within 8J degrees 

 of the pole, a similar flora existed, twenty-live species of fossil 

 plants having been collected by the last Arctic expedition, of 

 which eighteen are identical with the species from other Arctic 

 localities. This flora comprised poplars, birches, hazels, elms, 

 viburnums, and eight species of conifers, including the swamp 

 cypress and the Norway spruce ( Pinns abiesj, which last does 

 not now extend beyond 69£° N. 



" Fossil plants closely resembling those just mentioned have 

 been found at man y other Arctic localities, especially in Ice- 

 land, on the Mackenzie River in 65° N. Lat. and in Alaska." 



Thus it will be seen that proof in favor of the view that the 

 Arctic regions enjoyed a mild and equable climate unbroken 

 by periods of cold, up to and including the middle of the 

 Tertiary, is simply incontestable and overwhelming. At the 

 same time it is equally evident that while capable of support- 

 ing a luxuriant vegetation up to this period, the temperature, as 

 indicated by the fossil plants, shows unmistakable signs of a 

 slow and steady decline from a tropical to a temperate con- 

 dition. 



Let us next examine the evidence afforded by the plants as 

 indicative of former climatic conditions in the regions now 

 embraced within the North Temperate zone. Roughly speak- 

 ing, we now transfer our attention some two thousand miles to 

 the southward of these more typical localities in Greenland 

 which have furnished the remains of the remarkable flora here 

 discussed. Owing to more favorable circumstances and better 

 facilities, the deposits in these latitudes have been much more 

 extensively and thoroughly examined and their fossil contents 

 more carefully collected and studied, than those of the Arctic 

 regions. Moreover, we have in these deposits the remains of 

 large numbers of extinct animals often associated with those of 

 the plants, so that we are enabled to get a somewhat clearer idea 

 of its ancient physical conditions. But in attempting to corre- 

 late the results of investigation obtained in one region with 

 those in another, we have constantly to bear in mind the diffi- 

 culties which beset the problem of establishing equivalency in 

 the time scale in deposits of widely separated localities. We 

 are accustomed to depend very largely, if not solely, upon the 

 fossil contents of any two given strata for our ideas respecting 

 their equivalency in age. It has no doubt often happened, 

 however, that certain types of plants or animals originating in 



