PALEOGEOGRAPHIC CONCLUSIONS 467 



migrants, while beyond this barrier was, as we have seen, the per- 

 sistent Hamilton fauna which subsequently entered the New York 

 province to constitute the conservative element of the Ithaca fauna. On 

 the south were the extensive estuaries in which the black Ohio and 

 Genesee muds were being deposited, their depauperate and dwarfed faunas 

 indicating much dilution of the salt waters by the inpouring of rivers 

 from the south. These black muds can be traced continuously from 

 Maryland to Iowa, and as they are followed southward, or up the lateral 

 margins of the ancient lagoons, they are found to pass into similar, 

 though mostly undisturbed, terrigenous sands of Kinderhook or younger 

 age.^^ 



There is thus no possibility of deriving the Naples fauna from tlie 

 south, for here was a continuous land-mass. It follows that the only 

 available path of entry is the northern one, which, so far as our knowl- 

 edge of the formation is concerned, satisfies all requirements. True, the 

 Naples fauna has not yet been reported from Arctic America; but since 

 this is the only possible path of entry, and since the fauna is found in 

 Arctic Europe, we may confidently predict that, if fossiliferous Upper 

 Devonic formations are preserved in our arctic region, they will be found 

 to contain the Naples fauna. 



It is of importance to recall that the Hamilton fauna continued in that 

 portion of the Portage Sea which lay to the east of the Sherburne Bar, or 

 approximately in that portion of New York State now comprising Otsego, 

 Schoharie, Delaware, and Sullivan counties, on the south and parts of 

 Montgomery, Fulton, and Saratoga counties and the Champlain Valley 

 on the north. Thence the connection with the Atlantic was probably 

 along the general line of the Saint Lawrence, though the Gaspe region of 

 today was the site of continental sedimentation, as was the western 

 margin of Appalachia farther south. Southward this arm of the Atlantic 

 covered the region now included in the eastern counties of Pennsylvania 

 and that portion of New Jersey lying west of the Skunnemunk-Gree]i 

 Pond inlier of Paleozoics. The region of this inlier was the site of 

 lagoons in which the material of the Bellvale flags accumulated. The 

 section at Port Jervis shows that that region lay within the confines of 

 the embayment here outlined. How far south into eastern Maryland 

 this emba3^ment extended can not be determined, because the later 

 Paleozoic rocks have been wholly removed from that region by Post- 

 Paleozoic erosion. The preserved Devonic rocks of Maryland all belong 

 to the basin west of the Sherburne Bar. In any case, as before stated. 



37 A. W. Grabau : Types of sedimentary overlap. Bull. Geol. Soc. Am., vol. 17, pp. 

 567-636 [593 et seq.]. 



