NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 147 



RESTORATION OF THE REGION AND ENVIRONMENT IN WHICH THE 



ANIMALS LIVED. 



In the preceding descriptions only the better-known forms are included. 

 Many more are known from incomplete skeletons, solitary bones, or frag- 

 ments, which would not warrant any attempt at restoration. Probably 

 many more forms will be discovered in the Permo-Carboniferous beds, but a 

 large proportion of the faima may never be known. Enough has already 

 been made out to show that it was abundant and most complex. 



Considering only the region in Texas and Oklahoma, which is typical of 

 all the Red Beds, we may restore in imagination a great fiat land stretching 

 away from the Wichita Mountains and the Arbuckle Hills to the east and 

 south, where it joined the ocean waters. The western border of the flat we 

 do not know. The normally semiarid condition of the land was interrupted 

 by incursions of the sea and fluctuations of the climate to more humid condi- 

 tions. The aridity never attained a degree which prevented the growth of 

 some vegetation or the presence of pools of water and running streams, but 

 was sttfficiently intense, at times, to prevent the accumulation of much vege- 

 table debris in swamps or stagnant lagoons. In the times of increased 

 humidity the vegetation increased in quantity, the waters accumulated in 

 large areas and were overshadowed by a heavy growth, and the streams 

 expanded and spread over their flood-plains, leaving masses of irregularly 

 bedded sandstone and clay. It would perhaps express the ideas of the author 

 a little better to speak of the great flat as being particularly well drained in 

 the times of greatest aridity, with the water-table low, allowing a free cir- 

 culation of water and air. In the more humid periods the water-table rose, 

 and the circulation of the air and water was prevented. Even in the times 

 of greatest aridity it must be supposed that there probably were seasonal or 

 other changes of small period which brought enough moisture to keep the 

 land far from a true desert condition. 



Upon this flat, largely around the pools and streams, lived the wonder- 

 fully complex amphibian and reptilian life. The waters swarmed with fish 

 and amphibians, and were constantly invaded by predaceous reptiles in 

 search of food. In the quieter pools and back waters of the streams lurked 

 the great Eryops and its lesser relatives, ever ready to rush from their con- 

 cealment upon any unfortunate creatures that ventured too near. In the 

 open waters of the stream Cricotus opposed its strength to the current, 

 spending its time in active search and open attack upon its prey. Burrowing 

 in the mud, or creeping slowly along the slime at the bottom of the water, 

 were such forms as Lysorophus, Diplocaulus, and a host of forms with similar 

 habits. The slender Varanosaurus or Theropleura slipped qfiietly into water 

 and swam slowly until the sight of some victim caused it to leap into activity 

 and follow its prey with lightning speed at the surface or beneath the waters. 

 The banks of such pools and streams must have been arustle with the shifting, 



