264 W. N. LOGAN 
American fauna to the fauna of northern Eurasia: Belemnites 
panderanus d’Orb. and Lelemnites densus Mk.; Astarte duborsianus 
d’Orb. and Astarte pakardi White; Avicula volgensis d’O. and 
Avicula mucronata Mk.; Pentacrinus scalaris Goldf. and Penta- 
crinus astericus M. & H.; Gontomya dubois d’Orb. and Goniomya 
montanaensis Mk.; Gryphea calceola, Quen. and Gryphea caceola 
var. nebrascensis Mk.; Cardioceras cordatus Sow. and Cardioceras 
cordiforme Mk. The faunas taken as a whole exhibit the close 
relationship in a much more forcible manner than the comparison 
of a few species. 
This northern Eurasian, or Cardioceras fauna is thought to 
have had its origin on the northern shores of the Eurasian con- 
tinent, and to have migrated from there to American waters. 
This assumption is based on the sudden appearance of the 
fauna in America and its close affinities with older Eurasian 
faunas. The present geographic distribution of the fauna 
indicates a northern connection. 
A later Jurassic fauna, the ducella fauna, probably had its 
origin in the north and migrated to Pacific waters. This fauna, 
however, did not reach the interior province of America as the 
waters of the epicontinental sea had been withdrawn before its 
appearance. This later migration extended along the Pacific 
coast as far south as Mexico. 
Both of the faunas just mentioned belong to the Upper Jura, 
but the Lias and Middle Jura are also represented in the Cali- 
fornian province. The Upper Jura, however, represents the 
maximum encroachment of the ocean on the American con- 
tinent as well as on the Eurasian continent. It also marks the 
maximum expansion: of marine life, induced doubtless by 
increased feeding grounds. 
Connection of the sea with the ocean.— The question as to where 
the interior sea had its connection, or connections, with the 
ocean is important in estimating the extent of the submergence, 
That the sea had a Pacific Ocean connection there seems no 
longer room for doubt. The occurrence in the Queen Charlotte 
fauna of so many species common to the interior places the 
