l82 



THE ORIGIN AND EVOLUTION OF LIFE 



lateral swimming undulations, the limbs relatively useless. 

 Corresponding to the bottom-living fishes are the large, slug- 

 gish, broad-headed, bottom-living amphibians, such as Diplo- 

 caulus, with heads heavily armored, limbs small and weak, the 

 body propelled by lateral motions of the tail. There were also 



.^^^M^wm. 





.^\[,i/l,.)i L 





./, / 



Fig. 63. Amphibia of the American Permo-Carboniferous. 



Here are found the free-swimming Cricotiis, the short-bodied Cacops, and abundance of 

 the amphibious terrestrial type, the large, solid-headed Eryops. Restorations for the 

 author by W. K. Gregory and Richard Deckert. 



more powerful, slow-moving, long-headed, alligator-like, terres- 

 trio-aquatic forms, such as the Archegosaiirus of Europe and 

 the fully aquatic Trimerorachis of America. An extreme 

 stage of terrestrial, ground-living evolution with marked reduc- 

 tion of the use of the tail for propulsion is the large-headed 

 Cacops, short-bodied, with limbs of medium size, but with 

 feeble powers of prehension in the feet. Radiating around 

 these animals were a number of terrestrial types exhibiting 

 the evolution of dorsal protective armature and spines {Aspi- 

 dosaurus); other types lead into the pointed-headed structure 

 and pointed teeth of Trematops. 



