252 EEPORT OF THE AMERICAN COMMITTEE. 
Nova Scotia. ") 
New Brunswick. >- Millstone Grit Formation. 
Newfoundland. J 
This important division has been spoken of as the Conglomer- 
ate or as Millstone Grit, the great sandstone floor on which the 
Coal Measures rest ; but the division is too important, economi- 
cally and stratigraphically, to be buried under any such misno- 
mer as Conglomerate, Serai or otherwise. Nor should its coal- 
beds bespoken of as Intercongloraerate, for the including sand- 
stones are often far from being conglomerate. 
The upper limit is determined without difficulty throughout 
the Appalachian and Mississippi regions. In much of the 
former, however, the lower limit is somewhat indefinite, and is 
in the shales, referred by most authors to the Lower Carbonic. 
No such difficulty exists in northern Pennsylvania and Ohio, 
where the upper plate is the Homewood Sandstone and the 
bottom plate is the Sharon Conglomerate. In a general way, 
this structure can be traced on both sides of the Appalachian area 
into Tennessee, where the lower strata disappear and the Lower 
Carbonic limestones are brought up to the coal beds. A similar 
condition exists in the Mississippi river regions. 
THE LOWER CARBONIC. 
There is seldom any difficulty within the interior basin or the 
Appalachian area in determining the upper limits of the Lower 
Carbonic, but some uncertainty still prevails at many localities 
respecting the lower limit, that between the Carbonic and the 
Devonic. The difficulty, however, is lessening and the debatable 
zone is becoming narrower. 
Throughout the Appalachian region, the Lower Carbonic is 
double, the division being well defined on both physical and 
paleontological grounds. The correlations of these and the sub- 
divisions within the Mississippi valley have been determined but 
not in full detail. The following list shows the synonyms. 
Greenbrier. 
Synonyms and Local Subdivisions. 
Pennsylvania XI., Urabral, raost of; Mauch Chunk, most of; Slienango 
Shale (?) 
_ , . f Maxville Limestone. ) ,.. , ^ 
Ohio, i T o • r Vv averly Group in part. 
( Logan Series. ) 
