CLASSIFICATION AND FAUNAS SbS 



resulted from the inclusion in the Williamson of the true Sodiis shale, 

 which is now found to be markedly disconformable with it, and with 

 which it has almost no species in common (probably only .1 frypa reticu- 

 laris and Leptodesma rliomhoidca) . Chonetes cornuius, which at Eoch- 

 ester and Sodus always occurs on the same slabs as Monograptus and 

 Retiolites, is already listed as upper Clinton by Bassler (13:1487), as 

 also Monograptus. 



The transfer of the true Williamson to the upper Clinton makes but 

 inconsequential changes in Bassler's lists. Monograptus clintonensis and 

 perhaps Plectamhonites transversalis (that is, P. elegantulus) are erased 

 from the lower Clinton, while Leptodesma rliomhoidea is added to the 

 upper Clinton. Retiolites venosus and " Rhynchoyiella' (Camarotoechia) 

 emaceraia, with possibly Lingula (Palceoglossa) perovata, are also re- 

 moved to upper Clinton. In addition to these the following have been 

 inadvertently admitted to the lower Clinton list aiid must l)e transferred 

 to the upper Clinton-Rochester independently of the rectification of 

 boundaries here proposed : Atrypina disparilis and Nucleospira pisiformis 

 of the Rochester shale at Wolcott village and many other localities, Cyrtia 

 meta of the upper Irondequoit and Rochester, Pentamerus oralis and 

 Lingula twniola of the Phoenix-Herkimer, Palceophycus striatum of the 

 Brewerton, and probably also Kionoceras {suh) cancellatum of the Iron- 

 dequoit and Rochester. ''Holopea fragilis" should read TIelopora. 



While the dividing line between lower and upper "Clinton" thus grows 

 more clear cut, that between "Medina'^ and "Clinton" since the discovery 

 of the Medina age of the so-called Clinton of Ontario (Cataract) and 

 Ohio (Brassfield) correspondingly fades away. The same argument that 

 would include the Rochester shale in the upper Clinton would embrace 

 the Medina (excluding Queenston) in the lower Clinton. Neither one is 

 present in the type "Clinton" section. But faunally the affinities named 

 are unquestionably great, emphatically greater than those between lower 

 and upper "Clinton." In short, the major faunal and stratigraphic break 

 within the Eontaric is at the AVolcott Furnace ore and cleaves the "Clin- 

 ton" into two parts, one of which falls naturally into company with the 

 Rochester and the other with the Cataract-Medina, though each still re- 

 tains a minor individuality from either of these. The name Clinton, 

 like the "Silurian" of older writers, has been doing double duty. 



The writer is not prepared to oifer names for the combined "Lower 

 Clinton"-Medina and the "Upper Clinton"-Rochester, respectively lower 

 and upper Eontaric. Preferably these names should come from the thick 

 sections in Pennsyhania or Maryland. But it is interesting to note that 

 the four chief divisions now outlined (approximately Medina, lower 



