STRATIGRAPHIC TAXONOMY 673 



Following the general strike of the rocks, the Ceratopea zone is met 

 with again in the west foot of Frog Mountain on the Georgia-Alabama 

 line near Piedmont in the latter State. Here it underlies the Frog 

 Mountain sandstone supposed to be of Oriskany age. How far this out- 

 crop continues southwestwardly is unknown, but in the Cahaba Valley 

 the zone is persistent. At Pelham there must be at least 500 feet of 

 these Canadian limestones. Above them is a well developed middle Stones 

 Eiver section, beneath them the Chepultepec formation. These three for- 

 mations continue southward in this deep structural trough to the vicinity 

 of Montevallo, near which point Mr. Charles Butts estimates the thick- 

 ness of the Canadian part of the section at over 1,000 feet. This xAla- 

 bama representative of the Jonesboro differs sufficiently to make another 

 name desirable. It is therefore suggested that the term Pelham. which 

 as used by the Alabama Survey comprises chiefly Canadian limestones, be 

 restricted to it. 



Some may question the propriety of referring the whole of the lime- 

 stone series beneath the early Stones Eiver Mosheim limestone and down 

 to the top of the N'olichucky shale, in the vicinity of Jonesboro, Ten- 

 nessee, to the Canadian. In other words, it may be contended that the 

 evidence is insufficient on which these 2,250 feet of limestone are assigned 

 to a position in the time scale above the top of the typical Knox in 

 Tennessee (see page 548), and above the even younger Che])u1topoc for- 

 mation in Alabama. In answer to this probable objection T would say 

 that we know (1) that the Ceratopea fauna is confined in Missouri and 

 Arkansas to beds resting unconformably on the Jefferson City dolomite, 

 (2) that the Roubidoux- Jefferson City lies unconformably on the Gas- 

 conade. (3) that the Gasconade contains the Chepultepec fauna, (4) 

 that in central Alabama the Chepultepec overlies the tvpical Knox and 

 underlies the Jonesboro limestone, (5) that the Ceratopea fauna occurs 

 nearly 2.000 feet above the base of the Canadian section in Pennsylvania, 

 (6) that these 2,000 feet of limestone succeed unconformably a cherty 

 formation carrying the Chepultepec fauna, and, finally, (7) that the 

 interval between the N'olichucky shale and the Ceratopea zone in the 

 Jonesboro section is probably less and certainly not greater than the 

 pre-Ceratopea part of the Canadian section in Pennsylvania. 



On page 553 I stated that the time relations of the Jefferson City dolo- 

 mite to the lower part of the Canadian system in Pennsylvania is as yet 

 a matter of opinion. This admission was made because the two zones 

 have not been found superposed in the same section. Still, the case is 

 proved so far as faunal evidence and correspondence in thickness of 



