GEOLOGICAL PAPERS. 99 



pods, Dalmanella elegantula and Rhipidomella hybrida are com- 

 mon Niagara species; Gypidula simplex was described by Foerste 

 from the W'aldron bed at Newsom, Tennessee; Atrypa piitilla 

 was described by Hall and Clarke from very early Silurian strata 

 in Pike County, ^Missouri, which have been correlated with the 

 Edgewood^ formation in Alexander County, Illinois. Several of 

 the other species in this list, while not specifically identical with 

 forms occurring in the Edgewood formation of southwest Illinois, 

 have very close afiinities with species found in that formation. 

 These are shown in the following comparative table : 



Comparative Table of Fossils. 



Fossils from the Channahon Lime- Fossils from the Edgewood Forma- 



stone in Will County. tion in Alexander Countj\ 



Zaphrentis cJuinnahotiensis . Zaphrentis channahonensis 



Atrypa putillaF Atrypa putilla 



Dalmanella elegantula var. Dalmanella elegantula var. 



Leptaena rhomboidalis Leptaena rhomboidalis 



Rhynchotreta intermedia Rhynchotreta thebesensis 



Schuchertella curzistriata Schuchertella propinqua 



Whitdeldella acuminata IVhitHeldella billingsana 



Pterinea elegans Pterinea thebenensis 



Dau-sonoceras tcnuilincatum Dawsonoceras cf. tenuilineatum 



Cyphaspis intermedia Cyphaspis intermedia 



MetapoUchas ferrisi Metapolichas clintonensis 



Proetus channahonensis Proetus deierminatus 



While the correspondence of the respective species of fossils 

 compared from the two areas is not identical, yet the dilterences 

 between them are slight. The fauna from the Channahon locality 

 is more closely related to that of the Edgewood formation than to 

 any other known fauna. 



It is thought that the strata in the two areas represent about the 

 same general period of deposition; and that the dilterences in 

 the specific characters of the forms above compared are largely 

 due to local differences in the marine environments of the faunas 

 in the respective regions. 



Whether the sea in which the Channahon limestone accumu- 

 lated was connected southward with the Pike County, ^lissouri, 

 and Alexander County, Illinois, basin, or whether it had a 

 northern connection as did the sea in which the overlying Niagara 

 limestone was deposited, cannot be determined until other 

 exposures of these early Silurian beds are discovered and their 

 faunal relations are better known. 



iSavage, T. E. : 111. State Geol. Surr., Bull. No. 16, 1911. 



