THE PERMIAN PERIOD 393 



while others, such as the corals, were largely reorganized on 

 new plans. The change is seemingly one of the most abrupt 

 and profound in all the geologic record. Yet in northern 

 India and California, where the Permian seas lingered on 

 into the Triassic, the change in the fossils is gradual and no 

 sharp dividing line can be drawn. 



More ample opportunities for the land life. The very 

 changes which restricted the habitation of the corals, mollusks, 

 and their kin gave wider room to the denizens of the land. A 

 great abundance and variety of plants and insects were already 

 present. The salamanderlike types of amphibians were 

 even more numerous and better constructed than in the 

 Pennsylvanian. In fact, they were never afterward as promi- 

 nent as at this time. Amphibians nowadays are small crea- 

 tures, and most of them have soft bodies; but some of the 

 Permian types were large and were more comparable to rep- 

 tiles like the crocodiles of to-day with their bony-plated heads, 

 powerful muscles, and formidable array of teeth. 



Reptiles gain the ascendancy. It was left for the true 

 reptiles, however, to gain supremacy among the land animals 

 in the Permian period, in spite of their amphibian rivals. 

 When any group first appears in geologic history, it is apt to 

 be represented by closely related kinds unlike those which live 

 to-day. These are known as generalized types, because they 

 combine vaguely in one animal the characteristics of several 

 later kinds. Thus in the Permian there was one kind of rep- 

 tile which resembled in some respects the crocodiles, the 

 lizards, and other types now extinct, and yet cannot be 

 classed with any one of these groups more than with the others. 

 Later, these generalized types branched out into the distinct 

 forms now recognized. These will be described in connection 

 with a later period. 



Prevalence of arid climates. The abundance of salt and 

 gypsum beds in the Permian strata of many countries has 

 already been mentioned as indicative of desert conditions. 

 Deserts are, of course, only possible on land, and to-day they 



