LOWER CARBONIFEROUS FOSSILS. 491 



forms, often real Kinderhook types, which, however, do not pass over into 

 the highly developed and differentiated species belonging to the same genera 

 in the Mississippi Valley in Burlington time and later. 



On the other hand, several genera in the Madison limestone show by 

 their presence that we are not dealing with a pure Kinderhook fauna. 

 Here must be mentioned the genera Archimedes, Martinia, Seminula, and 

 Endothyra. Archimedes is not known below the Keokuk, nor Endothyra 

 below the "Warsaw. Species of Seminula have been described from the 

 Kinderhook, and Martinia is well represented in the Devonian, occurring 

 also in the Mississippian and Coal Measures ; but an experience of several 

 years in the Waverly group of Ohio and adjacent States seems to confirm 

 the statement that these genera are rare indeed in the Kinderhook fauna. 

 It is significant that in the Madison limestone Archimedes and Endothyra 

 are found only in the upper portion, while Seminula and Martinia range 

 throughout. 



Such species as Derbya keokuk (?), Camarophorid ringens, Camarotoschia 

 metalUca, and Eumetria verneuiliana demand individual consideration in 

 discussing the age of the Madison limestone. 



If Bhynchonella metalUca was really originally found in Upper Carbon- 

 iferous rocks, either it must have an extraordinarily long' range or else 

 this is an instance of the danger in making identifications on external 

 characters from a single specimen; for between the type and the material 

 from the Madison limestone I can find no specific distinction. 



Derby a keokuk (?), whose identification is based upon a single poorly 

 preserved specimen, is known in Indiana associated with Syringothyris 

 and a Waverly fauna. While Eumetria verneuiliana is characteristic of 

 the upper Mississippian, we find in the Kinderhook Acambona osagensis 

 Swallow, Hustedia triangularis Miller, Eumetria (?) altirostris White, Betzia 

 circularis Miller, B. plicata Miller, and B. popeana Swallow, all Retzioids 

 and of a more or less similar type. It is noteworthy that the form which 

 I have referred to Eumetria verneuiliana is confined to the lower beds of 

 the Madison. It may really be one of the species just mentioned, but in 

 its present condition can not be distinguished from the better-known form 

 with which I have identified it. Camarpphoria ringens was described from 

 the Burlington chert of Missouri, but the form which I have called by that 

 name is present in the Kinderhook fauna as well. 



