|EXTINCT FAUNAS OF THE MOHAVE DESERT, THEIR SIGNIFICANCE IN A STUDY OF THE ORIGIN AND EVOLUTION OF LIFE IN AMERICA|
IT is almost a rule that features of the natural world which have exerted an unusual influence in developing our emotional, poetic and religious natures, when brought within the range of scientific inquiry seem only more deeply to excite our wonder and respect. Thus, it has happened that the deserts of the world, having furnished the stimulus for some of our earliest poetic and religious literature, appear to the scientist of to-day as places in which nature meets us with unusual frankness, and where her wonders almost clamor to be understood.
In those fields of history covering the development or evolution of. the external form of the earth and of the life upon it, deserts have been very significant sources of information, and the so-called bad-land formations in the arid or semi-arid regions of western North America have been recognized as playing a very important part. As the widespread exposures of these formations have elsewhere in America proved veritable museums of wonderfully preserved remains, it has seemed worthy of remark that the extensive bad-lands in the Great Basin region of America have with few exceptions furnished almost nothing bearing on the history of life. The early geologic explorers in Nevada and California found little bearing on the paleontologic story of the area they examined. Later investigators in the bad-lands of these regions have generally failed to report determinable vertebrate remains, and the life record has until recently remained practically a closed book. It has been with much interest, therefore, that those concerned with the history of western North America, and with its bearing on the whole story of life growth or evolution, have seen coming to light with the past decade chapter after chapter of this missing record.
With the exception of the John Day region of eastern Oregon, which supplies an important geologic and paleontologic record, the largest part of our knowledge of the history of mammalian life west of the Wasatch is obtained in the heretofore unexplored deposits of the Mohave Desert. At the present time there are available from the Mohave at least three extinct mammalian faunas previously unknown, or only imperfectly known, in the Great Basin. The life record given us by these faunas, the evolutionary series to which they contribute, and the suggestions