THE RELATIONS OF SOME CARBONIFEROUS FAUNAS 7 



above the top of the true Chemung. The intervening beds 

 seem, therefore, to represent a new time interval between the 

 Devonian and the Carboniferous, for which the name Bradford- 

 ian has been suggested. 



The extent of the Bradfordian series, which includes beds 

 sometimes loosely termed " Upper Chemung," is not definitely 

 known, but the evidence thus far obtained indicates that the 

 Pocono and possibly part of the Catskill belong to it. If this is 

 true, and if the correlations summarized by Stevenson in the 

 report just cited, are in the main correct, this series plays an 

 important part in the geology of the Appalachian basin. 

 Therefore, in my view, which I hope shortly to support by a 

 complete presentation of evidence, the Pocono, if it actually 

 forms part of the Bradfordian series, instead of being equiva- 

 lent to the Waverly, as generally supposed, passes under it in 

 the vicinity of Warren, the real Waverly apparently not extend- 

 ing farther to the eastward. The Bradfordian series is fre- 

 quently exposed in Crawford and Erie counties, where it in- 

 cludes the Riceville shale and, doubtless, considerable thick- 

 nesses of the underlying beds. In Ohio it is tentatively assumed 

 to be represented by the Bedford and Cleveland shales, and 

 probably by the Erie. Its age is a matter of some diversity of 

 opinion, but I believe that its true relations are with the 

 Devonian. 



In the Central States the Mississippian series is usually suc- 

 ceeded by a bed of sandstone or conglomerate, followed by the 

 Coal Measures, and in many cases preceded by an erosional 

 unconformity. This basal sandstone, often called the "Mill- 

 stone grit" or " Coal Measure conglomerate," has always been 

 classed with the Upper Carboniferous, and has been regarded 

 as ushering in the Upper Carboniferous or Pennsylvanian. 

 Comparatively seldom does it contain fossils of any kind, and 

 never, so far as I am aware, invertebrate fossils. On this 

 account, and because it is not in this area of very great thick- 

 ness, it has generally been given little consideration by inverte- 

 brate paleontologists, the arena of whose investigations has been 

 largely confined to these North Central States. Nevertheless, 

 this horizon is probably destined to form a very interesting field 

 for paleontologic research. 



