12 NEW YORK STATE MUSEUM 



The lower beds are well exposed along the escarpment from the 

 large quarry 2 miles northeast of Clarence to Williamsville and 

 specially in both of those villages. The middle beds may be seen 

 along Ellicott creek at Bowmansville and in some field outcrops 

 and small quarries 2 miles north of Mill Grove, and the upper 

 strata in the bed of Ellicott creek for a mile or two west of Mill 

 Grove. At Bellevue what appear to be the uppermost layers of 

 the Onondaga limestone are exposed in the bed of Cayuga creek 

 north of the electric car line for 50 to 60 rods. The rock has been 

 quarried here and the exposure includes about 10 feet. There is 

 also a small outcrop of these strata in the south bank of the stream 

 a mile northeast. 



MARCELLUS BLACK SHALE 



This term has been generally applied to a series of black and 

 dark shales that immediately succeed the Onondaga and at the 

 top pass gradually into the lighter colored Hamilton shales. x\t 

 Marcellus, Onondaga county, from which locality the name is 

 derived, only the lower beds are well exposed and recent observa- 

 tions in that region and in the western part of the State indicate the 

 desirability of restricting the term to the lower shales exposed 

 at the type locality. 



Westward from Ontario county the Marcellus shale is clearly 

 delimited on the top by the Stafford limestone, the shale above 

 which, though very dark, is more calcareous and weathers to a 

 light gray, while the rock between the Onondaga and the Stafford 

 is a densely black and bituminous slaty shale with a few thin cal- 

 careous layers and, at some localities, a row of spherical concre- 

 tions usually one to two feet in diameter. 



On these quadrangles the Marcellus is 20 to 25 feet thick. 

 Fossils are common in the Marcellus shale at the base and for 

 3 or 4 feet at the top. Where this formation is more calcareous and 

 lighter colored they are fairly abundant. A list numbering 20 species 

 of those occurring in these beds at Lancaster may be found in New 

 York State Museum Bulletin 49. 



The following are the more abundant forms : 



Ambocoelia nana Grabau 



Chonetes mucronatus Hall 



Isochilina? fabacea Jones 



Liorhynchus limitare {Vaniixcm) 



Pterochaenia fragilis (Hall) 



Nuculites triqueter Conrad 



Orthoceras subulatum Hall 



Strophalosia truncata (Hall) 



Styliolina fissurella Hall 



I 



