l6 NEW YORK STATE MUSEUM 



two to ten rods across, occur in the horizon of the Tully limestone 

 so frequently as to appear at nearly every exposure of the Moscow- 

 Genesee contact. When freshly exposed the stratum is extremely 

 hard and refractory, but it softens and disintegrates in very old 

 exposures, its position in the walls of ravines being usually indicated 

 by a thin rust-colored band. 



Fossils of 48 species have been identified from this layer in On- 

 tario and Livingston counties. A full description of the pyrite 

 lentils and a list of its fossils may be found in State Museum 

 Bulletin 69, 1903. 



GENESEE BLACK SHALE 



Overlying the pyrite layer or, in its absence, the Moscow shale, 

 there is a bed of black bituminous shale similar in appearance to 

 the Marcellus shale 500 feet lower in the strata. As commonly used, 

 the term applied to these strata has included the succeed- 

 ing Genundewa limestone, the dark West River shale and the black 

 Middlesex shale above it. As here used, the term Genesee black 

 shale designates the strata between the Tully horizon and the 

 Genundewa limestone, which on these quadrangles have a total 

 thickness of 85 to 90 feet. The shales are mostly densely black and 

 contain a proportion of hydrocarbons sufficiently large to produce, 

 when freshly broken, a natural fetid odor. 



Pyrite in small nodules is common. Rows of spherical concre- 

 tions and a few thin flags of fine grained calcareous sandstone, also 

 occur. 



Fossils, except a few plant remains, are almost entirely absent 

 from the black shale and are rare in the lighter beds. The follow- 

 ing have been obtained from the Genesee shale in this region: 



Conodont teeth 

 Pleurotomaria rugulata Hall 

 Probeloceras lutheri Clarke 

 Bactrites aciculum {Hall) 

 Styliolina fissurella Hall 

 Pterochaenia fragilis (Hall) 

 Lingula spatulata Hall 

 Orbiculoidea lodensis Hall 

 Liorhynchus quadricostatus Hall 



Exposures of Genesee shalef may be found on the Honeoye 

 quadrangle in two ravines on the east side of the valley two miles 

 north of the village of Honeoye, along the Hemlock outlet one to 



