366 CHARLES S. PROSSER 



many as the Hamilton, and the Ithaca 52.8 per cent. This is not 

 remarkable, however, when it is recalled, in the first place, 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 

 Dr. John M. Clarke; and, in the second place, that the Ithaca fauna 

 is sequential to the Hamilton, and in the Ithaca region contains a 

 large percentage of Hamilton species. When followed to the east- 

 ward, 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 individ- 

 uals 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 above tabulation 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 compared with that which 

 exists between the fauna of the Maryland beds and the New York 

 Hamilton fauna. Restating the tabulation, then, it is shown that 

 there are more than twice as many entries common to the Maryland 

 and New York Hamilton beds than 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 midddle and 

 upper portions of the Romney formation, with the Hamilton beds of 

 New York. 



Recently Professor H. S. Williams has published an extended 

 account of what he calls the Tropidoleptus carinatus fauna of the 

 Hamilton formation.' Faunally he considers the Hamilton forma- 

 tion as including the deposits between the top of the Onondaga lime- 

 stone and the base of the Tully limestone of central New York, which 



I American Journal of Science, Fourth Series, Vol. XIII (1902), pp. 421-32; Bulletin 

 No. 210, U. S. Geological Survey, 1903, pp. 42-68. 



