DEVONIAN AND MISSISSIPPIAN FAUNAS 285 
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 Muscatine 
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, Airypa 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. 
