Claypole.] 494. [May 16, 
Beds so thin are not likely to be continuous over so great a distance. Such 
discrepancies are due to difference of conditions during deposition. They 
are no argument against correspondence. 
Pornts OF RESEMBLANCE. 
It is impossible to avoid noticing the close correspondence, in general, 
between the two sections looked at as wholes. The lower parts of the two 
sections are absolutely identical except in thickness. And in Perry county 
the lower portion includes 965 feet out of the 989 which represent the 
total mass. In New York it includes 62 feet 2 inches out of the total 80 
feet 6 inches. That is, practically, the column presents a close resem- 
blance in the two sections through three-fourths of its length in New 
York and through forty-nine fiftieths of its length in Perry Co., Pennsyl- 
vania. Closer correspondence could not be looked for. 
This reduction of its mass also brings the group in Pennsylvania into 
rather closer resemblance in thickness, to that which it possesses in New 
York. It is still vastly thicker, but this is the usual condition. If the 
whole of the shales of the fifth group be included the disproportion is 
enormous, 
The resemblance can be traced even into more minute detail. Prof. 
Hall describes the Lower green shale as consisting of thin smooth laminie 
containing lenticular masses of limestone. If sandstone be substituted 
for limestone, these words exactly describe the Lower green shale of 
Perry Co. Of the Lower limestone he says: ‘‘This mass is composed al- 
most entirely of thin beds of impure limestone which alternate with thin 
layers of green shale.” Again the change of the word will adapt the 
description to the iron sandstone and ore of Perry Co. Of the Upper 
green shale we read (p. 64): ‘This is readily distinguished from the 
Lower green shale by its being everywhere fossiliferous ;’’ a statement 
also true of the two shales in Pennsylvania, The Lower has yielded me 
almost nothing, while from the Upper I have obtained a fair collection. 
Stratigraphically, therefore, it is almost impossible to expect a closer 
agreement between two correlated beds than that which we actually find 
here. And unless contrary evidence be found elsewhere, it is not only a 
reasonable, but an inevitable inference that these beds must be considered 
equivalents. 
PALMONTOLOGICAL EvripENon. 
It is not possible at present to give in full the evidence furnished by 
palwontology in favor of the classification above adopted. The suspension 
or termination of the work of the survey in this department will delay 
for a considerable time the working out of the collection I have made and 
the making of a larger one. So far, however, as I have been able in the 
intervals of field work to study this material, it is decisively in favor of 
the views here set forth. A few details are appended, the parts of the 
group being taken in order, 
