GEOLOGY IN THE UNITED STATES 53 



or age of invertebrates; the devonian, or age of fishes, and the 

 carboniferous. Mesozoic time consists of but one age, the 

 age of reptiles. Cenozoic time is divided into two ages, the 

 tertiary, or age of manunals, and quaternary, or age of man. 

 This classification represents more than fifty years' indefati- 

 gable labor on the part of the paleontologists of Europe and 

 America. The impetus which the publication of Lyell's 

 Principles gave to the study of fossils has never abated, and 

 every available region in England, France, Germany, and the 

 United States has been thoroughly explored. An enumera- 

 tion of those who have contributed to this gigantic undertak- 

 ing would be but a mere catalogue of names. 



In America the progress of discovery and research has 

 been unparalleled, until it has become par excellence an 

 American subject. In 1859 Joseph Leidy discovered the 

 bones of a prehistoric quadruped in the basin of an ancient 

 Rock}^ mountain lake. A vigorous exploration of all the 

 older lake basins of Wyoming, Utah, New Mexico, and 

 Dakota revealed the fact that the western part of North 

 America had once been the home of mammoths, rhinoceroses, 

 tapirs, horses, and other quadruped animals. The two men 

 who have probably done more than any others to develop 

 American paleontology are Professor Marsh, of Yale college, 

 and the late Professor E. D. Cope, of Philadelphia, vertebrate 

 paleontologist of the United States geological sm^vey, both 

 men of immense fortune. From 1876 to 1885, Professor Cope 

 had from three to five expeditions always in the field, the 

 expenses of which he bore himself. When the fossil beds 

 of Kansas, Colorado, Dakota, and Wyoming, the greatest 

 known, were discovered. Professor Cope and Professor Marsh 

 assumed the mighty task of excavating, shipping, and classi- 

 fying these remains of the reptilian and mammalian ages. 

 Thirty seven species of serpents were found in Kansas alone, 

 varying from ten to eighty feet in length, and representing 

 six orders. Some of them were terrestrial in habit, many 

 were flyers, and the others inhabited the salt ocean. The 

 extent of the sea westward was vast and geology has not 

 laid down its boundary, but it has been conjectured to be a 

 shore now submerged beneath the waters of the North Pacific 



