224 J. P. Smith — Periodic Migrations. 



Desmoceras latidorsatum Miclielin. 

 Puzosia planulata Sowerby. 

 JTauericeras Gardeni Bailey. 

 Phylloceras Whiteavesi Kossmat. 



P. Velledae Michelin (cited as the probable 



equivalent of P. ramosum Meek). 



Besides the above, F. M. Anderson* describes the follow- 

 ing species from the lower Chico beds as identical with Indian 

 forms : Schloenbachia propinqua Stoliczka, S. blanfordiana 

 Stoliczka, Desmoceras sugata Forbes. Nearly all these species 

 that are common to the western coast of America and India 

 also occur in Japan, and many of them also in eastern Africa. 

 They are, then, tropical or subtropical in habitat. Whether 

 the appearance of the Aucella fauna of the 'Upper Jura and 

 the Lower Cretaceous in the North Pacific meant cold water 

 or not, the appearance of the Indian forms in the same region 

 can only be interpreted to mean that a warm temperature pre- 

 vailed there at that time, and that conditions were equable 

 around the old shore line from India as far as California. 



With the closing of the passage between Asia and America, 

 the warm Japan current, which is now chilled by the cold 

 southwesterly current from Bering Sea, would warm up the 

 whole coast line and make the waters of western America 

 warmer than they are now. We also have evidence that the 

 temperature of the land in the northern hemisphere was 

 warmer than at present, for Heerf has shown that the Creta- 

 ceous floras of Greenland, Spitzbergen and Alaska contained 

 cycads and other forms indicating a mean temperature of 

 about 70° F. 



Upper Chico. — In the upper Chico horizon (Senonian), of 

 California and Oregon the connection with India appears to 

 cease, and a path of migration from the interior Cretaceous 

 sea of America seems to have been opened. J Several species 

 of pelecypods are identical with species from the upper Mis- 

 souri province, and some of the ammonites are closely allied. 



Eocene. — During the early Tertiary, or Tejon epoch, in 

 California we have no evidence of any migration from Asia, 

 but it is plain that a connection existed with the Eocene sea 

 of the Atlantic region. Yenericardia planicosta, which is 

 abundant in the Claiborne beds of the states around the Gulf 

 of Mexico, has been found at a number of places in Oregon 

 and California, and it appears to be more common in southern 

 California than anywhere else on the western coast. Other 



* Cretaceous Deposits of the Pacific Coast, Proc. Calif. Acad. Sci. , iii, Ser. 

 Geol., vol. ii, No. 1, 1902. 



\ Flora Fossilis Arctica, vi and vii, 1882-83. 



% F. M. Anderson, Cretaoeous Deposits of the Pacific Coast, p. 59, 1902. 



