DEVONIC PERIOD 545 



the Mississippian sea. Here the Gulf faunas persisted in considerable 

 purity, and migrated around the Cincinnati axis into the western part of 

 the New York basin. New York state preserves the best record of these 

 eastern or Atlantic forms and the southwestern or Gulf waves of migrants. 

 Some of the characteristic species of the New York Hamilton, however, 

 appear somewhat earlier in the Jeffersonville limestone of the Indiana 

 basin. 



In the Cordilleran and Dakotan seas there is no evidence of Middle 

 Devonic faunas until near the close of this epoch. In the Manitoba re- 

 gion then occurs the String 'ocephalus burtini fauna in the Winnipegosan 

 series, which in Europe is found toward the end of the Middle Devonic. 

 The same brachiopod is- also found in southern Minnesota, in red residual 

 clay or geest. In Iowa the lower Wapsipinicon may belong to this time, 

 yet its fauna, though meager, seems to be rather of the early Upper De- 

 vonic type. 



Neodevonic. — Toward the end of the Middle Devonic the Gulf embay- 

 ment became closed, and about this time there appeared in Iowa a west- 

 ern fauna, that of the Cordilleran sea, which spread to the Kankakee axis 

 and through the Iowa and Traverse basins, connecting with the Mississip- 

 pian sea. However, it does not yet appear that much of this western life 

 invaded the eastern sea at any time during the Erian, Senecan, or Chau- 

 tauquan. Clarke thinks that the strange and decidedly European Portage 

 or Intumescens fauna migrated from the Cordilleran sea into the New 

 York basin, but to the writer its path seems to have been from the Atlan- 

 tic through the New Jersey strait. These forms may have distributed 

 themselves along the Atlantic shore of Appalachia into the Appalachian 

 trough, thence south to the shallow region of Virginia, then across to the 

 eastern shore of Alleghania, and so north into western New York. If 

 this path is not admitted to be the true one, the reverse must have taken 

 place, in which event the Intumescens goniatites came to New York from 

 the Cordilleran sea, developed in great generic and specific variety in the 

 western New York basin, and then migrated into the Atlantic and across 

 to Europe. It is hardly probable that the same genera developed twice 

 from the same primitive stock, both in New York and western Europe. 



The Appalachian trough served as the means of continuing the Atlantic 

 Hamilton faunas into the Ithaca and Chemung, and throughout this time 

 the New Jersey straits were open. In the northeastern end of the trough 

 the normal marine conditions gave way to vast estuarine flats of red muds,, 

 while the Ohio and Indiana basins had mainly changed to black seas, 

 owing to the cul-de-sac condition of this area. For these reasons the 



