M A U V A I S E S T B R R E S. 



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For a further and more detailed account of the comparative anatomy of the fossil 

 mammalia collected on this Survey, the reader is referred to Dr. Leidy's accom- 

 panying Memoir. 



The investigations connected with the geology of this curious country, and the 

 natural history of its ancient Fauna, are invested with no small degree of interest, 

 when we consider that, at the time these singular animals roamed over the Mau- 

 vaises Terres of the Upper Missouri, the configuration of our present continents was 

 very different from what it now is. Europe and Asia were then, in fact, no conti- 

 nents at all, being represented only by a few islands, scattered over a wide expanse 

 of ocean. The Atlantic seaboard of the United States, back to the mountain 

 ranges, and up the Valley of the Mississippi as high as Vicksburg, was yet under 

 water. Mount Etna, that remarkable volcanic cone of Sicily, nearly 11,000 feet in 

 height, was yet unformed, and the fertile plateau of that island, more than 100 miles 

 in circumference, was still deep under the Tertiary Mediterranean Sea. In Europe, 

 during the period following the extermination of the eocene Fauna of Nebraska, 

 the Alps have been heaved up nearly their whole height ; and in Northern India, 

 the whole Subhimalayan Range has been elevated. In South America, 9,000 feet 

 have been added to the height of the Cordilleras, and the South Atlantic has been 

 driven back 700 miles, while a district of country 2,500 miles in length, from the 

 Great Plain of the Amazons to the Straits of Magellan, has emerged from the ocean. 



Some of my readers, who have not made Geology a particular study, may be 

 curious to follow the course of reasoning by which geologists have arrived at such 

 startling results — results which must, no doubt, appear to them incredible. 



In Europe, in Asia, and both North and South America, science has long ob- 

 served and studied particular geological formations, which, in all these countries, 

 have a certain degree of uniformity of organic remains therein embedded. These 

 are, chiefly, an assemblage of marine shells and corals, which, though they differ, 

 in most instances, in trivial minutiae of form, yet bear a close resemblance to the 

 very shells and corals now inhabiting our seas, and which are cast by thousands on 

 our shores. 



It is not in a few rare instances alone, that these fossil shells are detected em- 

 bedded in the substance of the rocks in question ; many of the strata, and especially 

 those that contain much lime, actually teem with these exuviae ; and, not unfre- 

 quently, as in Florida and Mississippi, they are but an agglutinated aggregate of 

 marine productions. We have, indeed, the most unequivocal proof, that all the strata 

 composing this formation have been a succession of sediments or precipitates consoli- 

 dated at the bottom of the ocean. Alternating with these beds there are also others 

 interstratified, filled with the bones of quadrupeds which have perished on the 

 banks and near the mouths of rivers, whence they have been swept into estuaries 

 and bays, and entombed in the sediments there accumulating. In the occurrence 

 of such mammalian remains, the geological formations to which the attention of 

 the reader is now called, differ essentially from every other which underlies them, 

 and which, therefore, are of more ancient date ; since it is a self-evident fact, that 



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