Successive deposits in the Appalachian region 435 



as Orthorhynchula linneyi. I have not seen these specimens, but I ven- 

 ture the query whether these specimens may not be small forms of the 

 short -hinged gibbous Platystrophia lynx (ponderosa Foerste) var. steven- 

 soni Grabau. Undoubted specimens of this species are found associated 

 with Byssonychia of the richmondensis type in the Bays sandstone of 

 Tennessee, where I have collected them at Walker Mountain. Since the 

 fossils of the red sandstones are all molds (internal as well as external), 

 small specimens of the P. stevensoni may easily be mistaken for Ortho- 

 rliynchula linneyi or for Rhynchotrema capax. On the basis of the dis- 

 tribution of the fossils at Cincinnati, the Orthorhynchula would indicate 

 the Fairmount beds in the Lower Maysville, while the Platystrophia lynx 

 (ponderosa) would indicate the Mount Auburn or highest Maysvillian. 

 According to Schuchert's correlation, this would in the one case be late 

 Lorraine, in the other post-Lorraine and post-Oswegon as well. I am 

 satisfied that the latter is the correct correlation, even should the fossils 

 from Bedford County prove on critical examination to be Orthorhynchula. 

 Byssonychia radiata ranges through the Lorraine and the Richmond and 

 so is not of value in precise correlation. It is probable, however, that 

 the species is not radiata in the restricted sense, but belongs to the rich- 

 mondensis group, as is the case with the species from Walker Mountain. 

 The Blair County sections 50 of the Juniata also show an alternation of 

 shales and sandstones. In Tyrone Gap, where a good exposure of this 

 and the enclosing formations are found, the section comprises the follow- 

 ing beds in descending order : 



Feet In. Feet In. 



33. White sandstone 100 + 100 ± 



Possible base of Tuscarora. 

 32. Red sandstone, with layers of red shale from 6" to 5' 



thick 255 



31. Concealed interval 540 



30. Red massive sandstone 84 



29. Green slaty sandstone 1 8 



28. Red sandstone with a few layers of red shale 87 



— 007 8 

 27. Green slate t 6 



20. Red sandstone 10 



25. Red shale 5 



24. Green slate 5 



23. Red sandstone 5 



22. Gray sandstone 20 



21. Red shale 1 



20. Gray sandstone 10 



50 Report T on Blair County by Franklin Piatt, 1881, pp. IT and IT; also Report T :lt 

 p. 144. 



