Review of the New York Geological Reports. 301 



Ripple marks are beautifully preserved in the terminal grey 

 mass at Medina, in connection with the Dictuolites. 



No strata have as yet been discovered in the Western States 

 which can be identified with the Medina sandstone. 



Clinton Group. (A part of No. 5 of Pennsylvania and Vir- 

 ginia.)— From the variable character of the deposites embraced 

 in this formation, it was first described under the name of the 

 Protean group. In Pennsylvania it is known as the red and va- 

 riegated shales and sandstones. Such are its predominating fea- 

 tures, but interstratified with them are thin bedded impure lime- 

 stones and iron ore. 



Where it is well developed, as above the lower Genesee Falls, 

 the following divisions are distinguishable : — 



Feet. 



1. Lower green shale, - - - - 23-00 



2. Oolitic, lenticular or fossiliferous iron ore, - 1*20 



3. Pentamerus limestone of the Clinton group, - 14-00 



4. Second green shale, - _ _ 24-00 



5. Upper limestone of Clinton group,* - - 1840 



Total thickness of the united beds, - - 80-60 



The lower green shale and Pentamerus limestone form the 

 middle Genesse Fall ; the outcropping edges of the upper shale 

 and limestone are visible above this fall. 



The belt of country occupied by the Clinton group in New 

 York is limited. On the chart it is represented by a narrow 

 green band running nearly east and west, south of the Medina 

 sandstone, widest in Wayne County and near Lake Oneida, thin- 

 nest towards the west, extending from Sharon near the centre of 

 the state into Canada. 



The beds of iron ore are, in a practical point of view, the most 

 important part of this formation. There are two of them, sep- 

 arated usually by about twenty feet of calcareous shale. The 

 lower of these is most productive, and varies in thickness from 

 six inches to two feet. The upper is only worth working at a 

 few localities. It is supposed that this ore has originated from 

 the decomposition of iron pyrites and subsequent infiltration, into 

 its present position from the adjacent ferruginous beds. 



These ore beds are evidently of the same nature and occupy 

 the same geological position as the fossiliferous calcareous iron 



* Hall's Report, p. 67. 

 Vol. XLviii, No. 2.— Jan.-March, 1845. 39 



