THE STORY OF NINETEENTH-CENTURY SCIENCE 



compared to those generations that represented the real 

 childhood of our race. 



VI 



Coincidently with the discovery of these highly sug- 

 gestive pages of the geologic story, other still more in- 

 structive chapters were being brought to light in Amer- 

 ica. It was found that in the Rocky Mountain region, 

 in strata found in ancient lake beds, records of the 

 tertiary period, or age of mammals, had been made and 

 preserved with fulness not approached in any other 

 region hitherto geologically explored. These records 

 were made known mainly by Professors Joseph Leidy, 

 O. C. Marsh, and E. D. Cope, working independently, 

 and more recently by numerous younger paleontolo- 

 gists. 



The profusion of vertebrate remains thus brought to 

 light quite beggars all previous exhibits in point of mere 

 numbers. Professor Marsh, for example, who was first 

 in the field, found 300 new tertiary species between the 

 years 1870 and 1876. Meanwhile, in cretaceous strata, 

 he unearthed remains of about 200 birds with teeth, 600 

 pterodactyls, or flying dragons, some with a spread of 

 wings of twenty-five feet, and 1500 mosasaurs of the 

 sea-serpent type, some of them sixty feet or more in 

 length. In a single bed of Jurassic rock, not larger 

 than a good-sized lecture-room, he found the remains 

 of 160 individuals of mammals, representing twenty 

 species and nine genera ; while beds of the same age 

 have yielded 300 reptiles, varying from the size of a 

 rabbit to sixty or eighty feet in length. 



But the chief interest of these fossils from the West is 



114 



