452 C. JR. Keyes — Fauna below the Burlington Limestone. 



Phanerotinus paradoxus Winchell. 

 Gapulus paralius (White & Whitfield). 



Capidus formosus (Keyes) . 



JPorcellia nodosus Hall. 



Loxonema prolixa White & Whitfield. 



Loxonema sp.f 



Spherodoma penguis (Winchell). 



Pleurotomaria sp.f 



Holopea subconica Winchell. 



Murchisonia sp.f 



Pelierophon bilabiatus White & Whitfield. 



Straparollus ammon (White & Whitfield). 



StraparoUus luxus? (White). 



Omphalotrochus Springvallensis (White). 



The forms in the accompanying list are all species which 

 characterize the Kinderhook of Burlington, Iowa ; most of 

 them being originally described from that place. In addition 

 many more species of lamellibranchs, brachiopods and gastero- 

 pods occurring very abundantly at the latter locality are found 

 in the white chert of Louisiana along with a few of the Bur- 

 lington limestone species. 



It is to be noted that : 



(1) The fauna of this horizon is predominantly molluscan, 

 representing a marked contrast with that of the typical Bur- 

 lington limestone, which is prevailingly crinoidal, with some 

 brachiopodal forms. 



(2) The fauna is the typical one of the Kinderhook beds. 



(3) There is mingled with this fauna some of the forms 

 from both above and below, which are thus associated with the 

 species representing the typical lower Burlington limestone. 



Here, then, is a well defined Kinderhook fauna intercalated 

 in the Burlington limestone, with jn'actically no change of 

 lithologieal characters ; a lower fauna suddenly appearing in 

 the midst of a higher. This is the most marked instance of 

 the kind that is at present known in the Carboniferous of the 

 Mississippi Valley. Though the time separation is not very 

 great, the present case is a striking illustration of Barrande's 

 celebrated " doctrine of colonies," so clearly developed in the 

 S}^steme Silurien du Centre de la Boheme,* and so ably de- 

 fended in his " Defense des Colonies." 



It is not to be inferred, however, that during the short 

 supremacy of the lower fauna in midst of an upper there was 

 a complete extinction of the deposed forms; but rather that 

 owing to peculiar conditions the lower fauua merely displaced 

 the upper temporarily ; or pushed it aside into other districts 

 for the time being. 



*Vol. i, p. 13, (1852.) 



