MARYLAND GEOLOGICAL SURVEY Cxlvii 



common to more than one of the Maryland horizons 17 per cent are 

 also common to the Chesapeake of Florida at Alum Blnif and the Chipola 

 river. 



For reasons which have already been specified, the Miocene fauna of 

 southern Xew Jersey is regarded by me as mixed witli foreign elements 

 which have been mechanically incorporated with it during the progress 

 of denudation or by current action. Eliminating the doubtfully indi- 

 genous forms the remainder has much the aspect of the Calvert fauna of 

 ^Maryland with which, on stratigraphic grounds, there is much reason 

 to assimilate it. 



In making comparisons with Virginia horizons we are met at once 

 with the difficulty that no good modern lists of Virginia Miocene mol- 

 lusks are available. To remedy this deficiency I have had tlie identified 

 species from Virginia localities in the National Museum collection listed 

 and have used them in making the following comparisons. Though 

 these Virginia species comprise little more than half of those which occur 

 in the horizons listed (many being yet unidentified), yet the numbers 

 seem sufficiently large to ensure the approximate accuracy of the percent- 

 ages derived from them. The lists comprise 71 species from Petersburg, 

 55 from the James river, 118 from the York river near Yorktown, and 

 57 from the newest beds of the Miocene near Suffolk, Va. The order 

 in which they are cited is that of tbeir relative age beginning with the 

 oldest. The following table shows the proportion of surviving species in 

 each of the mentioned horizons : 



Virginia — Petersburg horizon 8.5 per cent 



Maryland— Calvert formation 9.3 " " 



Virginia— James river beds 11.0 " " 



Marjdand — Choptank formation 11.4 " " 



Maryland— St. Mary's formation 12.1 " " 



New Jersey — Shiloh marls (mixture of 



faunas) 13.0 " " 



Florida— Alum Bluff horizon 14.0 " " 



A^irginia — -Yorktown beds 17.0 " " 



Virginia— Suffolk beds 19.0 " " 



North Carolina— Duplin beds 20.0 " " 



