I20 STUART WELLER 



DISCUSSION 



PROFESSOR CALVIN 



The paper presents very fairly and fully the taxonomic relations of the Devo- 

 nian and the Mississippian so far as Iowa is concerned. I should be disposed to 

 question the propriety of correlating the Sweetland Creek shales of IMuscatine 

 County with any part of the Kinderhook. It is true that in Missouri beds which 

 have been referred to the Kinderhook furnish Ptyctodus and some other Devonian 

 types; but at Burlington the Kinderhook shales carry a fauna that, in practically 

 all its aspects, is Carboniferous. On the other hand, the fauna of the Sweetland 

 Creek shales is characteristically Devonian. Leaving out Ptyctodus, which may 

 belong to either of the two formations, all the other life forms will be found to 

 be distinctively Devonian. The Sweetland Creek beds furnish two species of 

 Synthetodus, a form very common in the State Quarry limestone. Now the 

 State Quarry limestone is in large part made up of imperfectly comminuted shells 

 of that most intensely non-Carboniferous of all the Devonian types, Atrypa reticu- 

 laris, with occasional shells of another almost equally intensely Devonian form, 

 Gypidula comis. Fossils are rather rare in the Sweetland Creek beds, but all 

 that have been noted are such as to exclude this formation from any close relation 

 to the Kinderhook. 



