Hollick (1936:11) has described a rich early Tertiary Alaskan flora strikingly different from that of the same region at the present time. Composed of genera now characteristic of warm-temperate to subtropical climates, it was remarkable in having many types of plants that are now most characteristic of the North American hardwood forests in the southeastern part of the continent. Besides such widespread genera as _Fagus_, _Betula_, _Ulmus_, _Platanus_, _Castanea_, _Corylus_, _Carpinus_, _Crataegus_, _Spiraea_, _Myrica_, _Smilax_, _Pinus_, _Picea_, and _Abies_, this flora included others now characteristic of both warm-temperate southeastern North America and Eastern Asia, as _Magnolia_, _Nyssa_, _Sassafras_, _Persea_, _Benzoin_, _Hamamelis_, _Liquidambar_, _Celastrus_, _Nelumbo_, and _Onoclea_. It included genera _Carya_, _Taxodium_ and _Comptonia_ that now are limited to SE North America, _Sequoia_, now limited to western North America, and also included several genera which at present are limited to southeastern Asia: _Ginkgo_, _Glyptostrobus_, _Cinnamomum_, _Hausmannia_, _Artocarpus_, _Dillenia_ and _Koelreuteria_. This fossil flora provides strong evidence that in the early Tertiary climatic and habitat conditions as far north as Alaska were favorable for the existence of an ancestral _Eumeces_ similar to the modern _E. fasciatus_, which might have given rise to both North American and Asiatic members of the _fasciatus_ group. There is abundant evidence for the existence of an Eocene land connection between Alaska and northeastern Siberia, permitting free interchange of faunas between the two continents, as shown by the almost simultaneous appearance of various mammalian groups in the fossil records of Asia and North America. Simpson (1947:627) has summarized the evidence that such intermigrations were occurring throughout most of the Tertiary, with occasional interruptions as in middle Eocene, and in middle and late Oligocene, and with increasing selectivity, chiefly a progressive tendency toward screening out of the groups less tolerant of cold (judged on the basis of their modern representatives). In the late Tertiary, and especially in the Pleistocene, animals known to have made migrations between North America and Asia were types now characteristic of boreal climates (_e. g._ pika, hare, vole, lemmings, marmot, jumping mouse, fox, wolverine, bear, moose, caribou, sheep, bison, camels, mammoth). Simpson believes that there was fairly strong climatic selectivity even in the Miocene interchanges, and he indicates several important groups that were non-migrants in the Miocene, most of them remaining so through the Pliocene and Pleistocene--the primates, Rhizomyidae, Gliridae, Viverridae, Hyaenidae, Dicerorhininae, Suidae, late Anthracotheriidae, Hippopotamidae, Tragulidae, Muntiacinae, Lagomerycidae, Giraffidae, and Bovidae. He states that there is good evidence that these are all mainly warm-climate animals which are not