ORIGIN OF MAN AND THE OTHER VERTEBRATES. 611 



order, which occupied the earth at one (an early geological) period. 

 As reptiles are inferior to mammals in the scale, so they are of earlier 

 origin. The primitive reptilian order first appeared in force on the 

 earth during the Permian epoch that populous time which immedi- 

 ately followed the age of the true coal. If it existed during the coal- 

 measures proper, it has not yet been found in them in North America. 

 This order has been named the Theromorpha. Its representatives 

 have been found in Russia, Germany, South Africa, Illinois, Texas, 

 and France. I give the names in the historic order of discovery. It 

 embraced both carnivorous and herbivorous forms, and species of sizes 

 from that of the Malayan tapir downward. Those with piercing teeth 

 occur everywhere, and those with grinding teeth in North America 

 only. South Africa furnishes us with genera with leaf -shaped teeth, 

 and others with no teeth at all. This order represents the first air- 

 breathing land-population of vertebrates, and they evidently fulfilled 

 most of the functions of the mammalia of to-day, though none of them 

 were fliers, so far as known. Many of them had strange physiogno- 

 mies, with blunt noses and large nostrils, and long teeth mingled with 

 other smaller ones. Besides having given origin to most of the rep- 

 tilia, this order presents many points of resemblance to the mammalia. 

 Some of the bones resemble very closely those of the duck-bill or Pla- 

 typus of Australia, and some of the bones of the skull are more mam- 

 malian than the corresponding parts of any other reptiles. It is prob- 

 able that the lowest order of mammalia, which is to-day represented 

 by the duck-bill (the Monotremata), were derived from the Thero- 

 morpha. (See " Proceedings " of the American Association for the 

 Advancement of Science for 1884.) 



The different lines of reptiles have been traced less completely 

 than those of the mammalia, partly because their history is more 

 ancient, and the formations where their remains are preserved have 

 suffered greater disasters. The changes that have appeared with ad- 

 vancing time have been in the bones of the shoulder-girdle and pel- 

 vis, in the limbs, vertebra?, and skull. Certain changes in these parts 

 resulted in the appearance, in the period immediately following the 

 Permian (the Triassic), of the orders of the sea-saurians, the flying 

 saurians, and the land-saurians or Dinosauria. In the next period, 

 the Jurassic, we have the first certain knowledge of the tortoises and 

 lizards ; while, in the following ages of the Cretaceous, we get the 

 pythonomorphg and the snakes. All of the existing orders were in 

 the world by the beginning of Tertiary time, but the great monsters 

 that characterized the middle period of the earth's history were only 

 represented by the crocodile branch of the Dinosauria. 



The changes of structure which these several lines underwent in 

 the course of the ages were quite different from those which the his- 

 tory of the mammalia exhibits. Instead of becoming more perfect 

 organs of locomotion, the limbs, if we except those of the flying rep- 



