558 POPULAR SCIENCE MONTHLY 



THE DAWN OF QUADRUPEDS IN NORTH AMERICA 



BY Dr. ROY L. MOODIE 

 THE UNIVERSITY OF CHICAGO 



IN the early days of the physical sciences one who gave a common- 

 sense interpretation to a phenomenon of nature was looked upon 

 as dissenting from the accepted interpretation of things. It pleased 

 the people of the early days of science to regard natural phenomena 

 as something wonderful, as a divine creation or as something beyond 

 the comprehension of the human intellect. It has been less than two 

 centuries since men began to emerge from under this pall. The ad- 

 vance made in science constitutes one of the wonders of the age. It is 

 the purpose of this essay to record the progress of investigation in one 

 line of scientific research, and that is the one which leads up to a 

 knowledge of the ancestry of one group of the vertebrates. 



The early observers of nature had curious suppositions in regard 

 to the nature of fossils. They regarded these objects, which were 

 common, as of various origins. Some claimed that they arose spon- 

 taneously in the rocks, others were of the opinion that they arose from 

 germs which had fallen from heaven, but the large majority believed the 

 fossils to be the remains of " an accursed race " whose existence had 

 been ended by the Noachian deluge. Early in the seventeenth century 

 collectors of natural objects became familiar with certain bodies which 

 were known as " glossopetrse." They were embedded in the rocks and 

 the manner of their entombment was a matter of considerable dispute. 

 In the first half of the seventeenth century, Fabio Colonna had tried 

 to convince his contemporaries that the " glossopetrse " were nothing 

 but shark's teeth. His arguments failed to carry conviction, however. 

 It was not until 1669 that Steno, a Dane by birth, though a teacher in 

 the schools of Florence, Italy, demonstrated by the dissection of a com- 

 mon shark's head that the " glossopetras " and the teeth of the shark 

 were identical. These results he published in a quaint little volume 

 entitled " De Solido intra Solidum naturaliter contento." 1 This was 

 the first application of the modern method of paleontological research 

 to the study of objects contained in the rocks. Later Cuvier continued 

 and extended the researches of Steno and from the time of the famous 

 investigator, Cuvier, to the present, our knowledge of the objects 

 entombed in the rocks has progressed rapidly. 



Modern researches have carried our knowledge of the distribution 



1 Huxley, T. H., 1881, " Science and Hebrew Tradition Essays," p. 29. 



