100 



The Middle Devoxiax Deposits of Maryland 



found that the Marcellus has 44.3 per cent as many as the Hamilton and 

 the Ithaca 52.8 per cent. This is not remarkable, however, when it is 

 recalled first, that a large percentage of the species in. the Marcellus shale 

 of New York continue into the Hamilton beds of that state, as has been 

 shown by Clarke ; second, the Ithaca fauna is sequential to the Hamilton 

 and in the Ithaca region contains a large percentage of Hamilton species. 

 When followed to the eastward and after the disappearance of the Tully 

 limestone and Genesee shale in the Chenango Valley, the writer has shown 

 that a still larger number of the Hamilton species lived into Ithaca time, 

 although part of them were represented by simply a few individuals which 

 were the last feeble representatives of their species. These rare indi- 

 viduals have been recorded in the range of the species making the faunas 

 of the Hamilton and Ithaca beds of New York seem more closely related 

 than they actually are and the same is true regarding the faunas of the 

 Maryland beds and the Ithaca beds of New York. This explanation is 

 sufficient to show that the table gives full expression to the closeness of 

 the relationship which exists between the fauna of the Maryland beds and 

 the faunas of the Marcellus shale and Ithaca beds of New York as com- 

 pared with that which exists between the fauna of the Maryland beds and 

 the New York Hamilton fauna. Eestating the tabulation then, it is 

 shown that there are more than twice as many entries common to tlie 

 Maryland and New York Hamilton beds as to the Maryland and New 

 York Marcellus ; and nearly twice as many for the Maryland and New 

 York Hamilton beds as for the Maryland and New York Ithaca. There- 

 fore the paleontological evidence strongly supports the correlation of the 

 Maryland beds, which represent in general the middle and upper portions 

 of the Eomney formation, with the Hamilton beds of New York. 



An examination of the tables shows that the following number of species 

 of the Hamilton beds of Maryland occur also in the formations of New 

 York. 



Number of species occurring in the Onondaga of N. Y. 17 



Marcellus " 47 



Hamilton " 92 



" '■ Sherburne " 10 



Ithaca " 55 



Chemung " 18 



