Marylaxd Geological Survey 43 



hamiUoncnsis, Spirifera mucvonaius, S. granulifcra, and Lelorliynclius 

 limitaris. This is a Hamilton group fauna, but the stratigraphic range 

 of Hamilton group equivalents in the Eomney shales is not apparent, and 

 Hamilton deposits probably extend some distance above." ^ Later it ■will 

 be shown that this formation in northeastern West Virginia and western 

 ^Maryland consists of the Onondaga and Marcellus shales and the Hamil- 

 ton stage of New York as shown by its stratigraphic and f aunal characters. 

 In other words it is equivalent to the Onondaga and Hamilton series of 

 the older New York classification. 



"Whether all of the Eomney formation succeeding the Marcellus shale 

 belongs in the Hamilton stage or not is uncertain owing to the fact that 

 the upper limit of the Eomney was not clearly indicated in the original 

 description, the statement being made that " Hamilton deposits probably 

 extend some distance above " shales in which Hamilton species were 

 collected.' 



The eastern line of the Piedmont folio crosses the Potomac Eiver not 

 far west of Iveyser, while the western belt of the Eomney formation of 

 Allegany County crosses the river at that locality and extends up the 

 New Creek valley of West Virginia into tlie area of the Piedmont folio. 

 In the description of the Eomney shales in this folio it is stated that 

 " the upper members contain alternations of thin, pale-brown or dark- 

 buff, sandy beds, which constitute beds of passage into the next succeed- 

 ing formation. 



" The vertical range and stratigraphic position of these passage-beds 

 appear to be somewhat variable, so that there is no definite line of 

 demarcation between the two formations [Eomney shales and the succeed- 

 ing Jennings formation]. Owing to this fact no pi-ecise thickness can 

 be assigned to the Eomney shales, and on the map the Eomney and 

 Jennings patterns have been merged to indicate the intergrading of the 

 two formations." '' 



In Allegany County at the top of the Hamilton shales is another black, 

 fissile shale which contains the fauna of the Genesee shale of New York 



^ Am. Geol., VoL X, pp. 17, 18. 



= Geol. Atlas U. S. Piedmont Folio (No. 28), 1896, p. 2, col. 2. 



