lOO STUART WELLER 



shale. As regards the relations of these three formations Calvin says :' 

 "The three units referred to the Upper Devonian — the Sweetland 

 Creek shales, Lime Creek shales, and State Quarry limestone — do not 

 he one above the other, but each is locally developed and lies uncon- 

 formablv on the Cedar Vallev Hmestones." 



The lower beds of the Wapsipinicon stage, other than the Inde- 

 pendence shale, do not furnish any considerable fauna, Martinia suh- 

 iimhona being the most conspicuous species, but the higher beds, as 

 well as the succeeding Cedar Valley beds, are abundantly fossiliferous, 

 and faunally the dividing-line between the Wapsipinicon and Cedar 

 Valley stages presents no more conspicuous break than that between 

 the successive beds included within the Cedar Valley. 



In correlating these faunas of the lowan Devonian with those of 

 the Eastern Continental Province, difficulty is met with because of the 

 few points of contact between the two faunas. The faunas in the two 

 provinces are so distinctly different that we are forced to the conclusion 

 that there could have been no free communication between the two 

 regions, but that they must have been entirely separated during the 

 whole or the greater part of Middle Devonian time by some barrier, 

 probably a land mass. During Upper Devonian time there was much 

 more in common between the lowan and New York faunas, showing 

 that communication had been established ere that time. In the corre- 

 lation of the faunas in the two provinces the important point to deter- 

 mine is the time of the establishment of this communication. Wil- 

 liams^ has shown that the Cuboides fauna of the Tully limestone in 

 New York is a distinct immigrant fauna from the Eurasian province, 

 probably by way of the Mackenzie Valley and Iowa. The character- 

 istic species of this fauna is Hypothyris cuboides, a species which is 

 represented in the lowan faunas by Rhynchonella intermedia Barris, 

 the lowan form apparently being specifically identical with the New 

 York species. In Iowa this species is limited in its range to the upper 

 portion of the Wapsipinicon stage, where it is highly characteristic of 

 one of the divisions of the Favette breccia,^ and where it is associated 

 with Gypidula comis. Because of the limited range of this species in 



I Jour. Geol., XIV, 575; also la. Geol. Surv., XVII, 197. 



^ Bull. G. S. A., I, 481-500. 



3 Norton, Iowa Geol. Rep., IV, 160. 



