and its Lower Oriskany Fauna. 431 



Limestone" of southern Illinois, Alexander, Jackson, and 

 Union Counties. From this region are known but 11 species, 

 and 8 of these are also found in Tennessee. They are Anoplia 

 nucleata, Anoplotheca flabellites, Eatonia peculiar is, Spirifer 

 worthenanus, S. hemicyclus, Megalanteris condoni, Amphi- 

 genia curta and Strop host ylus cancellatus. 



The " Clear Creek limestone" of Illinois is intimately con- 

 nected with the Lower Helderberg below, and is not less than 

 200 feet thick, being followed by a " quartzose sandstone " 

 from 40 to 60 feet in thickness. The latter is probably equiva- 

 lent to the Upper, or typical, Oriskany of New York, and 

 does not appear to be present in western Tennessee. From 

 Professor Safford's description of the Camden chert, it is evi- 

 dent that the Lower Oriskany thins rapidly southward. In 

 Tennessee, it is about 60 feet in thickness, while it is not less 

 than 200 feet thick in Illinois exclusive of the Upper Oriskany, 

 which is entirely absent in the former state. 



The "Camden chert" fauna contains 32 species, and 6 

 of these are restricted to southern Illinois and western Ten- 

 nessee. Of the entire fauna, 24 species are found either in 

 the Lower Helderberg or in the Lower Oriskany of other 

 regions, and 20 occur in the Upper Oriskany or Corniferous. 

 After removing the 13 species common to both the Lower and 

 Upper Oriskany, and the two restricted forms, IT remain. Of 

 these 10 occur either in Lower Helderberg of Lower Oriskany 

 rocks of other regions, while 6 are found in higher beds. This 

 evidence, therefore, indicates clearly a Lower Oriskany age for 

 the " Camden chert " of Tennessee and the " Clear Creek 

 limestone" of Illinois, which indication is the more marked 

 because of the absence here of such characteristic Upper 

 Oriskany species as Hipparionyx proximus, Chonostrophia 

 complanata, Spirifer arenosus, Rensselceria ovoides, Meristella 

 lata, Camarotozchia pleiopleura, C. barrandei, or C. speciosus. 



Lower Oriskany fauna of the Camden Chert of Camden, Benton 

 County, Tennessee. 



In Lower In Upper 



Oriskany Oriskany 



elsewhere, elsewhere. 



Zaphrentis roemeri Hall ? L. H.* 



Pholidops terminalis Hall X X 



Hipparionyx proximus Vanuxem ? A very 



small specimen if this species X X 



Chonetes mucronatus Hall ? _ _ X 



" melonica Billings X X 



Chonostrophia reversa (Whitfield) U. H. 



* L. H. = Lower Helderberg ; U. H. — Upper Helderberg. This list is based 

 on the collection in the U. S. National Museum. 



