STRATlGKAnilC TAXOKOMY 621 



fairly uniform. Moreover, torsion of the land mass lying to the south- 

 east of the Appalachian A'alley belt of folding is suggested by the fact 

 that middle Cambrian troughs containing Pai'adoxides were developed in 

 New England. The character of the movements and the probable cause 

 of this torsion could be readily explained, but lacking space this discussion 

 must be deferred. 



Middle Cambrian deposits in the Appalachian Valley. — The deposits 

 in southeastern Pennsylvania referred to the middle Cambrian begin 

 with the red and purple shales and calcareous sandstone of the Waynes- 

 boro formation, in all about 1,000 feet thick, and end with the limestone 

 and shales of the Elbrook formation, which is about 3,000 feet thick. 

 The section has been recently described by Stose in the Mercersburg- 

 Chambersburg folio. The Waynesboro is, in part at least, the equiva- 

 lent of H. D. Campbell's Buena Vista shale in central Virginia, of M. E. 

 Campbell's Eussel formation in southwestern Virginia, and of Keith's 

 Watauga shale in northeastern Tennessee. The Eome formation of 

 Tennessee, Georgia, and Alabama likewise is believed to correspond in 

 general with the Waynesboro, Eussel, Buena Vista, and Watauga forma- 

 tions. The latter two formations may include older beds than are to be 

 found in the Eome. Further, the middle part of the Montevallo in Ala- 

 bama, perhaps the upper and lower parts as well, is correlated with the 

 Eome. The upper part of the Montevallo possibly includes beds repre- 

 senting the Eutledge limestone in Tennessee, the lower part of the 

 Honaker limestone in Tennessee and southwestern Virginia, the lower 

 part of the Natural Bridge limestone in central Virginia, and the Elbrook 

 formation in Pennsylvania and Maryland. The basal part, on the other 

 hand, may locally include representatives of the Apison shale and Beaver 

 limestone. 



The time relations of these Appalachian formations to the typical 

 Acadian deposits in New Brunswick and Newfoundland have not been 

 accurately determined. The Protolenus zone in the latter is probably 

 older than the Eome, but not necessarily lower Cambrian. The Para- 

 doxides zones, also, I regard as older than the Elbrook and Eutledge. 

 Indeed, it would not surprise me if they proved older than the Eome, 

 though at present inclined to place them in the same stage as the Eome. 



It remains to be said of the Eome that certain, perhaps but locally 

 developed, fossiliferous beds which have been referred to the upper Eome 

 on none too sharply defined lithologic grounds may, in fact, belong to 

 the upper Cambrian. The fossils in these beds are chiefly of species 

 found in the Conasauga above them in the same areas and also in the 

 Eogersville and Nolichucky shales in northeastern Tennessee. On the 



