GEOLOGICAL RELATIONS OF THE POCONO 43 



Squaw sandstone, etcetera West Virginia. 



Lower Knobstone Kentucky. 



Absent in most of Tennessee and Alabama. 



II. Catskill (of Vanuxera) Eastern Pennsylvania. 



Hampshire of Darton Virginia. 



Absent in Western Pennsylvania, Ohio, Kentucky, most of West Virginia, 

 Tennessee, and Alabama. 



III. Chemung and Chemung-Catskill of^ , ^ ,.,^11 



I. C. White, Chemung of gteven- I ^^^^^^'^^^^^"^^ Maryland, and 



son, Jennings of Darton j ^ 



Riceville and Venango of I. C.White. North western Pennsylvania. 



Erie shale of Newberry Ohio. 



Absent Tennessee and Alabama. 



Grainger shale of M. R. Campbell. .Southwestern Virginia and Northern 



Tennessee. 



Tlie correlation is not exact ; the details available thus far enable one 

 to make but approximation. Of the names applicable to the upper 

 part of the Pocono, perhaps Logan is the best, as it is the most compre- 

 hensive and is the oldest, having been used by Professor Andrews in 

 1870.* No one of the terms used for the upper division of the Devonian 

 can be taken as a name for the whole, as each one of them has been 

 applied to a definite portion. The limits of the Catskill were set 

 definitively by Vanuxem, but the name had been used earlier by 

 Mather to cover rocks extending from the upper Silurian to the top of 

 the Devonian ; it has been used since to designate a condition, and 

 wherever red rocks have been found in the upper Devonian they have 

 been regarded, for this reason, as Catskill. The name has led to serious 

 confusion stratigraphically as well as paleontologically, so that the fishes 

 Holoptychius and Bothriolepis and the plant Archeopteris jacksoni have 

 been spoken of as Catskill fossils, whereas they belong far down in the 

 true Chemung. Mr N. H. Darton's term Hampshire will have to be 

 employed instead of Catskill. There is less objection to retention of 

 the name Chemung, yet it has been used with indefiniteness. Perhaps 

 the slate may be as well rubbed off to begin anew with the name Jen- 

 nings, offered by Mr Darton and already accepted by the United States 

 and Maryland surveys. 



The chief defect of the correlation is in respect to the Catskill or 

 Hampshire; yet correction is extremely difficult, at present impossible. 

 The lowest member of Doctor I. C. White's Oil Lake group in northwest 

 Pennsylvania is the Cussewago sandstone, a flat pebble conglomerate 

 resting on his Riceville shales, which are Chemung. This conglomerate 



* E. B. Andrews : Report of Progress, Ohio Geol. Survey, 1870, p. 62. 



