1883.] Oby [Claypole. 



some moclificatiou of these data time will show. As the lines ot discrimina- 

 tion are now drawn, this sandstone must therefore be placed in the Ponent 

 Group of Pennsylvania, and on palseontological evidence in the Catskill 

 Group of New York. And no future changes can raise it. Any alteration, 

 if made, can only lower it by placing it in the underlying or Chemung 

 (Vergent) Group. 



These details are necessary as an introduction to the facts and argument 

 which follows. 



Among the numerous fossils of the Kingsmill sandstone (many of which, 

 though casts, are in excellent preservation, often showing the finest detail 

 of structure), is one which at an early stage of the work arrested my at- 

 tention. Its beautiful condition and the immense number in which it 

 occurs were sufficient for this purpose. It is no exaggeration to say that at 

 some of the exposures this fossil occurs in millions. 



For some time I could get no clue to its name. At length, however, 

 after going through with care all the material in my possession or within 

 my reach, that bore upon the subject, I became almost certain that it Avas 

 a fossil figured by Professor Hall in the geology of the Fourth District 

 of New York, under the name Gypricardia rhombea. Possible inference* 

 from this determination, however, deterred me from making use of the 

 conelusion, and I laid the matter aside for further consideration. 



Returning to the subject during the winter, while engaged in the study 

 of my summer's collection, I found no reason whatever to distrust my pre- 

 vious determination, but in order to obtain the confirmation of another 

 observer, I enclosed a specimen in a small parcel which I had occasion to 

 send to Professor Whitfield, of the American Museum of Science, re- 

 questing his opinion on the identification. In his reply, he said : 



" The shell sent is, I think, without question, ScMzodus rhombeus Hall 

 ( Cypricardia rhombea) of the Fourth District Report. We have no really 

 authentic specimens here, they being all in Professor Hall's hands at 

 present." 



In order to make the identification perfectly certain, I packed up a speci- 

 men, and sent it to Prof. Hall, with a request for his opinion upon it. In 

 reply, he writes under date of March 10th, 1883. 



"I do not perceive any important difference between the specimen sent, 

 and ScMzodus rhombeus, though I have not before had the casts of the 

 interior, which I am glad to receive." 



There remains therefore no doubt that the specimens here alluded to be- 

 long to the species ScMzodus rhombeus Hall, of the Geological Report of 

 the Fourth District of New York, where it was described and figured 

 under the name of Gypricardia rhombea. It was found four miles north of 

 Panama, Chautauqua county. New York, and attributed to the conglom- 

 erate at the base of the Carboniferous system. This opinion is now proba- 

 bly held by few or by no one. Prof. Hall said in the Twenty-third Re- 

 gent's Report (p. 10) : 



"In the original collections of the Geological Survey, some of the con- 



