Birds and Mammals 



at present these ancient species are placed with 

 the marsupials, or pouched animals, and in the 

 subdivision called Polyprotodontia (many front 

 teeth), the one which contains our common 

 opossum. The specimens indicate small quad- 

 rupeds ; the jaw of Dromatherium is but nine- 

 tenths of an inch long, and the small, sharp- 

 pointed teeth say that they were either carni- 

 vores or insect-eaters. This is practically all that 

 can be said of the Triassic mammals of North 

 America. * 



When we come to the Jurassic, however, we 

 find as associates of the great dinosaurs numer- 

 ous small mammals, utterly insignificant, so far 

 as size goes, in comparison with those huge 

 beasts ; and if the dinosaurs had been capable 

 of thinking at all, they would probably not 

 have given their diminutive contemporaries a 

 first thought, to say nothing of a second. And 

 yet the one type was on the decline, while the 

 other was starting on a career that would bring 

 it to the first place in the animal kingdom. 



The early mammals are, with rare excep- 

 tions, known only from their teeth and im- 



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