LIFE 497 



the late Paleozoic retreated and gave rise to the early provincial 

 faunas of the Mesozoic. 



In each of these three areas an important remnant of Paleozoic 

 sra life seems to have undergone a radical and perhaps rapid evolu- 

 tion, such as might be anticipated from the crowding of the great 

 faunas of earlier times into limited areas. From these areas the 

 new faunas spread when the sea again extended itself upon the land. 



The most complete record of the transition from Paleozoic to 

 Mesozoic marine life is found in India. Beds containing fossils 

 characteristic of the Permian are overlain conformably by beds con- 

 taining forms characteristic of the Mesozoic. In the Permian beds 

 there are forms foreshadowing the Mesozoic types, and in the beds 

 above there are Permian types that lived on and mingled with 

 Mesozoic forms. The transition fauna of the Mediterranean region 

 appears to have been less rich. Concerning the early stages of the 

 Siberian fauna, little is known; but its peculiarities, as revealed in a 

 later stage of the early Trias, leave little doubt of its independence 

 of origin. 



It is quite certain that there was at least one other area where 

 important fauna! reorganization took place, for a notable fauna 

 appeared suddenly in the Middle Triassic, which does not seem to 

 have originated in any of these three districts. 



Geographic suggestions of the faunas. The alliance of the Indian 

 forms with those of North America is so close as to indicate that 

 before the close of the early Trias, migratory connections had been 

 established between India and western America. 



Somewhat later in the early Trias there appeared in the Siberian 

 region (Olenek River) a fauna having some of the same genera as 

 the Indian. Closely related species are found in Idaho. If there 

 was connection between the Indian and Siberian regions, it would 

 be possible for Indian species to reach America from Siberia either 

 by way of the Arctic coast, or by the Pacific sea-shelf, and slight 

 changes, involving submergence or emergence in the region of Bering 

 Strait might change the combination of the faunas. 



The Indian and Siberian provinces seem to have been distinct 

 from the Mediterranean province throughout the earlier Triassic; 

 but in California a few fossils have been found which are character- 

 istic of the earlier Triassic of southern Europe. 



The early Triassic faunas of central Europe were very diverse, 

 a part being developed apparently in fresh water, a part in isolated 



