1022 



NEW YORK STATE MUSEUM 



are calcareous and concretionary. Spherical concretions are 

 numerous, and some of them are 1 foot to 3 feet in diameter. 



The dugway roads leading down to the bridge at North 

 Evans were excavated in the black Rhinestreet shale, and all 

 of this formation is exposed in detail in the bottom and sides 

 of the Eighteen Mile creek gorge between North Evans and 

 the Erie Railroad bridge, 4 miles to the southeast. It is 185 

 feet thick in this section and is composed principally of bitu- 

 minous black shale, but there are several layers of bluish 

 shale, some of which are 6 feet to 8 feet thick, and in these 

 lighter beds there are many large septaria and beautifully 

 symmetric concretions. 



In two or three rows in the upper part of the band the septaria 

 reach a diameter of 6 feet to 10 feet and are 2 feet to 4 feet 

 thick. The lighter layers contain a few fossils like those found 

 in the Cashaqua beds. 



The black slates are almost barren, except of plant remains, 

 which are quite common. In the cliff at North Evans a small 

 Lingula occurs in one of the lower black layers. 



These shales are exposed at several places along the lake 

 shore on the north side of Sturgeon point and along the railroads 

 in the vicinity of Derby. 



A concretionary layer 6 inches to 8 inches thick, the upper 

 surface of which is a scraggly mass of angular fragments of 

 impure limestone, separated by thin seams of spar, like the sur- 

 face of a flat septarium but finer, is taken as the top of the 

 Rhinestreet shale, the proportion of black shale above this hori- 

 zon being less than the lighter. It is exposed under the Erie 

 Railroad bridge over Eighteen Mile creek below Eden Valley 

 and near Angola, and on the lake shore. 



The lighter shales that succeed the Rhinestreet shale are ex- 

 posed in a small ravine that comes into the gorge of Eighteen 

 Mile creek from the east about 60 rods above the Erie Railroad 

 bridge. The section covers about 100 feet, in which there are 

 many large and small spherical concretions and others that are 

 oblong and flattened. Very few of them are septaria. 



This horizon is strntigraphically continuous with the Hatch 

 shales and flags of eastern sections, but its lithologic characters 

 have changed somewhat. 



