Keyes — Devonian & Carboniferous in Upper Mississippi Valley. 365 



farther northward in the same state. The cephalopods are 

 represented by large forms of Cyrtoceras, Goraphoceras and 

 Phrasmoceras. One belonging to the latter genus may prove 

 to be Winchell's P. expansum. Another very characteristic 

 phase of the fauna is the non-trilobitic crustaceans, of which 

 a very considerable number have been found. They have very 

 close aflSnities to Tropidocaris and Amphipeltis. 



It appears, then, that the Devonian fauna characteristic of 

 the region extends up to the top of the Hannibal shales in 

 Northeastern Missouri, at Louisiana especially, and that the 

 argillaceous " Kinderhook " shales of southeastern Iowa, as 

 typically developed at Burlington and corresponding in great 

 part to the Hannibal shales, appear to carry no other remains 

 than those of pronounced Devonian types. The upper part 

 of the section usually regarded as Kinderhook at Burlington, 

 in fact all the thin limestone and sandstone bands down to 

 the main body of shale, may be now more properly regarded 

 as the equivalent of the Chouteau limestone, that is the upper- 

 most member of the so-called Kinderhook in Missouri. 



3. One reason why the fauna of the Chouteau (original) 

 limestone has not been better understood in its relation to the 

 faunas occurring lower in the so-called Kinderhook, and higher 

 in the Burlington limestone, has been that in the localities 

 where the lower Carboniferous has been most thoroughly and 

 widely studied, that is, along the Mississippi river, the Chou- 

 teau, as commonly recognized, nowhere crops out along the 

 great stream, except perhaps in the vicinity of the town of 

 Louisiana, where, under the typical Burlington, there is an 

 earthy limestone 6 to 12 feet thick, which has been consid- 

 ered a part of the latter but which is now believed to be the 

 attenuated edge of the Chouteau or its equivalent. At any 

 rate, in the same vicinity the undoubted Chouteau attains a 

 thickness of 15 to 30 feet. 



Below is a table showing (1) that none of the species come 

 up from below to the base of the Chouteau, (2) those start- 

 ing in the Chouteau, and ranging upward, (3) the fauna 

 starting in the basal member of the Burlington limestone, and 

 (4) the species which comprise a lower fauna in the midst of a 

 higher. 



