THE TRIASSIC PERIOD. 



53 



tical with those of India and others closely related to them. These 

 probably belong to a little later stage than their Indian relatives and 

 suggest that the sea-border tract of the North Pacific was the route 

 of migration from India to 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, but not the particular species common to the Indian and the 



iBsp 



d e f h g i 



Fig. 345. — A Group of American Marine Triassic Fossils. Cephalopoda : a, Cera- 

 tiles whitneyi Gabb; b, Orthoceras blakei Gabb; c, Meckoceras. Pelecypoda: d, Mya- 

 cites humboldtensis Gabb; e, Corbu'n blakei Gabb; /, Myophoria alta Gabb; h, Tere- 

 bratula deformis Gabb. Brachtopoda: g, Pecten humboldtensis Gabb; i, Rhyncho- 

 nella cequiplicata Gabb. 



Vladivostok fauna, and hence it is inferred that the Siberian-Indian 

 connection was later than the Indian-Vladivostok. There seems 

 also to have been some form of connection between the Siberian 

 province and the Idaho embayment, for forms closely related to 

 those of Siberia are found in Idaho. After the Indian-Siberian con- 

 nection had been made, it would be possible for Indian species to 

 reach America either by way of Siberia and the Arctic coast, or by the 

 Pacific sea-shelf, and slight changes involving submergence or emer^ 

 gence in the region of Behring Strait would change the combination 

 of the faunas. It was of course theoretically possible for some species 

 to have been carried by currents across the Pacific without following 

 the shallow-water zones, but this is improbable for all. 



The Indian and Siberian provinces seem to have been distinct 

 from the Mediterranean province throughout the earlier Triassic. The 

 Mediterranean fauna was distinguished by many species of Tirolitince, 



