THE TRIASSIC PERIOD. 55 



the Mediterranean Trias. It, however, still embraced types that 

 appear to have been related to the Siberian forms, from which it is 

 inferred that a connection had been established between the western 

 coast and the Mediterranean province, while a connection with the 

 Siberian region was still retained, but that the Siberian and Mediter- 

 ranean regions were still not directly connected. 



The later Triassic faunas. — During the later stages of the Triassic 

 period, a rather rich marine fauna flourished in California. A large 

 number of its species were identical with or closely allied to species 

 that abounded in the Mediterranean (Alpine) region. Many were 

 also common to the Himalayan region, from which it is inferred that 

 these provinces were in free communication with the west American 

 coast. On the other hand, the Upper Trias of British Columbia con- 

 tains a quite different fauna, containing a type that belongs to the 

 Siberian group. The British Columbian fauna is perhaps to be regarded 

 as the descendant of the Idaho fauna of the earlier Trias, with addi- 

 tions from Siberian sources, while the California fauna is perhaps a 

 derivative from the Mediterranean and Himalayan provinces by some 

 different route. It has been suggested by James Perrin Smith that 

 this was an Atlantic route, but the traces of the fauna along the route 

 are wanting, owing to the burial of the Triassic marine deposits along 

 the north Atlantic coast. A migratory route by way of Australia, 

 New Zealand, Antarctica, and South America is among the theoretical 

 possibilities. 



As already indicated, present knowledge is not sufficient to show 

 the precise nature of the migrations between Europe, Asia, and America 

 during Triassic times, and the suggestions that have been made must 

 be held subject to revision. As developed in America, the special 

 faunas are not ample enough to fairly represent the life of the time, 

 and a general sketch disregarding geographic limits is here substituted. 



General nature of the fauna. — The earliest fauna was markedly 

 restricted. In some degree this may be more apparent than real on 

 account of the imperfection of the accessible record, but in the main 

 it was undoubtedly real and due to the physical limitations already 

 sketched. At the same time, there was an increase in the relative 

 degree of differentiation. The conditions which repressed the life, 

 while they reduced the number of individuals, species, and genera, 

 forced them to diverge more and more from one another to accommo- 



