752 C. 0. Dunbar — Stratigraphy and Correlation 



doni, Atrypa reticularis (var. with very large growth 

 lamellae), Spirifer duodenarius, 8. acuminatus, S. hemi- 

 cyclus, S, worthenanus, Reticularia fimbriata, Metaplasia 

 pyxidata, Pentagonia unisulcata, Leptocoelia flabellites, 

 Phacops cristata, and Dalmanites myrmecophorus. In 

 the higher layers exposed on Buffalo River were f onnd in 

 addition Rhipidomella cf. penelope and Spirifer macro- 

 thyris. 



The relation of this fauna to that of the Clear Creek 

 chert of Illinois is very close. Of the forty-two species 

 identified from Tennessee, twenty-four occur in Illinois 

 and iive more have close affinities which will probably 

 prove to be identities. Even these numbers, however, 

 fail to express the close resemblance of the faunas, for the 

 twenty-nine species just noted embrace practically all 

 those of frequent occurrence in either fauna. 



In seeking to compare the fauna with those of the 

 Oriskany and the Onondaga, about one-fourth of the 

 species must be eliminated, because they are indigenous 

 and peculiar to this southwestern embayment, so that 

 their stratigraphic importance is not known. Seven 

 additional species range through both Oriskany and 

 Onondaga and may therefore be eliminated from consid- 

 eration. Of the remaining nineteen, four are elsewhere 

 confined to the Oriskany and twelve to the Onondaga. 

 The assemblage here of such characteristic Onondagan 

 species as Chonostrophia reversa, Centronella glans- 

 fagea, Spirifer duodenarius, S. acuminatus, Pentagonia 

 unisulcata, Phacops cristatus, and Dalmanites myrmeco- 

 phorus, is of the highest significance, and since this is 

 corroborated by the facts that the Camden is separated 

 by an interval of erosion from a normal development of 

 typical upper Oriskany, which it overlies, and that it 

 passes without a break into a recognized Onondaga for- 

 mation (the Grand Tower of Illinois), the conclusion 

 becomes inevitable that it belongs with the Onondaga in 

 the Middle Devonian. 



The distribution of this formation in Tennessee and 

 Illinois, and possibly Arkansas (the Arkansas novacu- 

 lite), the absence of the formation from the Appalachian 

 trough, and finally its faunal affinities with the Middle 

 Devonian of South America, already pointed out by Schu- 

 chert (1906), all indicate that it represents a southern or 

 Gulf embayment. The species which show a close rela- 



