STRATIGRAPHIC RELATIONS OF THE OXEIDA CONGLOMERATE 35 



fossil and the stratigraphic relations of the Oneida conglomerate 

 as shown in the Mohawk valley can leave no doubt of the upper 

 Medina age of the Oneida conglomerate. 



The presence of the fossil Arthrophycus alleghan- 

 i e n s i s Harlan in Pennsylvania, Maryland and Virginia is 

 •of special interest. Vanuxem 1 in referring to Pennsylvania says : 



There this fossil appears in the same position, and in sand- 

 stone of like diversity of character as to color, etc., as in New 

 York generally. It is abundant on the Juniata, and on the west 

 branch of the Susquehanna. I found this remarkable fossil in 

 Virginia, about 15 years ago, near the top of the Flat-top moun- 

 tain, a little to the west of the Salt valley above Abingdon. It 

 was in white sandstone, which caps that mountain, and which 

 rests upon a red sandstone reposing upon a gray or olive cal- 

 careous sandstone containing numerous testaceous fossils, refer- 

 able rather to those of the sandstone shale of Pulaski [=Lorraine], 

 than to any other part of the New York system. 



The later work by Stevenson 2 also shows that this fossil is 

 found in the upper Medina of Pennsylvania. 



In Maryland 3 the lower portion of the Medina is known as the 

 Juniata formation and the upper portion as the Tuscarora forma- 

 tion. No fossils are mentioned as coming from the former and 

 Arthrophycus is the only one mentioned as occurring in the 

 latter. 



The Tuscarora is regarded as, " perhaps nearly identical with 

 the White Medina of the Pennsylvania and New York surveys." 



In Wills Creek gorge in Maryland, Professor Schuchert 4 

 has constructed the following descending section for the Medina. 



1 Tuscarora. Snow-white to light gray quartzite, in places a 

 fine conglomerate ; Arthrophycus harlani the only 

 fossil — 287 feet. 



.2 Juniata. Interbedded dull red sandstones and shales. In 

 Wills Creek gorge 530 feet can be seen, but the total thick- 

 ness, on the basis of that in Bedford county, Pennsylvania, 

 is probably not less than 730 feet. 



3 " Hudson River shales." 



From the above it will be seen that the fossil Arthrophy- 

 cus alleghaniensis Harlan, wherever known, is most 

 characteristic of the upper Medina and appears to be practically 

 confined to this horizon and that from both stratigraphic and 

 paleontologic reasons, the Oneida conglomerate is to be con- 

 sidered as a part of the upper Medina. 



iGeol. N. Y. 3d Dist. 1842. p. 71. 



2 2d Geol. Sur. Pa. Rep't of Progress. T2. 1882. p. 91. 



3 Md. Geol. Sur. Allegany Co. 1900. p. 86. 



4 U. S. Nat. Mus. Proc. 1903. 26: 424 



