30 NEW YORK STATE MUSEUM 



Bactrites a c i c u 1 u m (Hall), Probeloceras lutheri 

 Clarke, Pteroc'haenia fragilis (Hall) and Buchiola 

 retrostriata (von Buch) occur in the lower beds and in the 

 shaly layers throughout the formation. A thin calcareous seam in 

 a sandstone 125 feet above the base of the formation exposed by th 

 side of the dugway road }^ mile east of Starkey station contains : 



Leptrostrophia mucronata (Con- Sp. laevis Hall 



rad) Cladochonus 



Spirifer mucronatus Conrad var. Crinoid stems 



posterus Hall & Clarke 



The higher sandstones on Breackneck creek at North Hector an( 

 on Lodi creek contain in addition : 



Ambocoelia umbonata Hall Choiiele? lepidus Hall 



Cyrtina sp. Honcoyea major Clarke 



Productella spinulicosta Hall 



II 



and Liorhynchus quadricostatum Hall occurs in the 

 sandstones at Ovid and several other species of brachiopods in the 

 quarries in this horizon near the east line of the quadrangle. ajA 



Rhinestreet shale 



In the region about the south end of Seneca lake and westward 

 to Lake Erie this shale succeeds the Cashaqua shale with a thick- 

 ness of 165 feet. It is represented on this quadrangle by 2 feet of 

 black shale, in the ravine of Plum creek half a mile west of Him- 

 rods. It appears at the Big -Stream ravine at Glenora, but is not 

 recognized on the east side of the lake on these quadrangles. It is 

 a well defined feature in the stratigraphy of western New York and 

 is more fully described in Museum bulletins 63, 81 and loi. 



Hatch shale and flags 



This formation is the stratigraphic equivalent of the lower 

 Gardeau beds in the Genesee river section and consists of a series j 

 of shales and sandstones aggregating about 350 feet in thickness. 



The shales range from black to light blue and from hard sandy 

 or slaty to soft and blocky, and there are frequent layers of hard 

 blue sandstone from 2 inches to 2 feet in thickness occurring at 

 irregular intervals, some of which are continuous for long distances 

 without change of character or thickness, while others thin out or 

 become shaly and disappear in a few rods. The lower beds of this 

 formation are much softer than the upper Cashaqua beds and in 



