>'(i i/(i8 of Sea and Air 



rine invertebrate. . . . Here ended not only the 

 living species of dinosaurs, of mosasaurs and 

 pterosaurs, but these tribes of reptiles." * 



Thus the competitors of mammals were 

 swept out of existence and they were left free 

 to develop. 



* Dana. Manual of Geology, edition of 1896, p. 876. 



219 



