310 STUART WELLER 



American species. European species. 



S. lineahis Martin. ) 



S. lineatoides Swall. > S. lineahis Martin. 



S. ftseudolineatus H . ) 



S. suborbicularis H. S. ovalis Phill. 



S. temiimarginatus H. S. duplicicostus Phill. 



Syringothyris carteri H. Syringothyris cusftidatiis Martin. 



The similarity between the faunas of the two regions is so 

 great that some way of intercommunication must have been in 

 existence. The presence in Grinnell Land r of a similar fauna, 

 in some respects intermediate between the two, would seem to 

 indicate a northern and then eastern passage-way between the 

 interior American province and western Europe. 



The physical changes, which initiated the interior continental 

 province of Osage time, were of a different nature from the 

 changes that had ushered in previous epochs in the history of 

 the region ; and as a consequence, the fauna of the Osage epoch 

 falls into a different category from earlier ones. In no case 

 were the changing faunas of the Appalachian province during 

 Devonian time, to any great extent, indigenous in their origin. 

 The Osage fauna, however, was apparently very largely native 

 to the region. The western European faunas doubtless exer- 

 cised their influence upon it, but the influence of the American 

 fauna upon that of Europe seems to have been much the greater. 



A large portion of the territory occupied by the Osage prov- 

 ince had previously been dry land. A vast area of new sea bottom 

 was formed by the sinking of the land. The marine organisms 

 which were to inhabit the region were unhindered in their devel- 

 opment. They came in contact with no previously existing 

 fauna which had either to be driven out or to be absorbed into 

 their own social organization. Their rapid growth and differ- 

 entiation may be compared with the rapid development of a 

 human civilization in a newly opened country with vast resources, 

 where there is a place for everyone with strength and vigor, and 

 where the close struggle of individual with individual does not 



1 Q. J. G. S. Lond., XXXIV, p. 568. 



