The problems of organic evolution have many aspects and ramify into many fields of science. The subject was at first embraced chiefly in the field of the old-time naturalist—zoologist or botanist—but the problems of variation and heredity have passed into the hands of the experimental evolutionist; and there are other problems whose answers are found in the geologic record, but these are of two rather opposite aspects. On the one hand, the paleontologist specializes particularly on the succession and relation of fossil faunas or floras. On the other hand, it is the field of physical and historical geology to restore the ancient environments. The relations of the environments to the biotas is a field wherein physical geology and paleontology meet, to give a better understanding of the underlying causes of organic response and progress. It is from the standpoint of physical and historical geology rather than from . . .