Introduction 



the Fishes and again and again in various combinations with the 

 Reptiles. They were first recognized as a group distinct from 

 both Fishes and Reptiles in 1804/ and were then called Batrachia. 



There is now no question but that the Batrachians, no mat- 

 ter how they differ in form, are closely related to one another 

 and are descendants of the Fishes. Neither is there any question 

 that in the past ages some primitive forms of Batrachians, now 

 extinct, formed the direct ancestors of the Reptiles. An under- 

 standing of their relation to other animal races has been facilitated 

 by the discovery of fossil remains of Batrachians and Reptiles. 

 Fossil Batrachia — the Stegocephali^ — have been found which 

 by the structure of the skeleton show evidences of descent from 

 either the Dipnoi or Crossoptergii (extinct Fishes). Fossil Rep- 

 tiles — Proreptilia and Theromorpha ^ — have been discovered 

 which in their turn seem to produce a gradually traced line of 

 evolution from these extinct Stegocephali to higher Reptiles. 



The Stegocephali are found in largest numbers in the Car- 

 boniferous strata of North America and Europe. They thus 

 must have flourished during the Coal Period in North America, 

 that early epoch in the history of the earth following the Age of 

 Fishes and preceding the Reptilian Age. At this time, the conti- 

 nent, which extended from what is now the Appalachian Moun- 

 tain region west to Kansas and Nebraska only, was in a semi- 

 emerged condition. The great areas of marsh were filled with 

 jungles and rank growths of fern and conifer, with an animal life 

 represented by many of the lower invertebrate forms (among 

 them some of the lower insects), and by the vertebrate classes 

 of the fishes, these early batrachians (the Stegocephali) and a 

 few of the early reptiles. But there were no flowering plants, 

 no moths, or butterflies, bees, or wasps; and the great silence was 

 unbroken by bird or mammal. That the Stegocephali did not 

 flourish much beyond this Coal Period is proved by the fact 

 that their remains are found in ever smaller numbers from the 

 lower Permian (at the close of the Carboniferous era) through 

 the Trias (of the Reptilian era), and that above this, their repre- 

 sentatives are almost wholly lacking. 



1 Brongniart, " Essai d'une Classification Naturelle des Reptiles." 



2 Stegocephali (Cope); Labyrinthodontia (Huxley). The latter represents the former in part 

 only. 



3 The fossils which have been assigned here may prove to be Stegocephalian instead of 

 Reptilian. 



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