22 NEW YORK STATE MUSEUM 



Exposures. This black shale is exposed in the ravine west of 

 Alexander; above and below the railroad bridge at Griswold; be- 

 low the railroad bridge a mile west of the station at Darien Center, 

 and at a 5 foot fall in Durkee creek, 3 miles southeast from Alden, 

 where the entire section with an interbedded row of spherical con- 

 cretions and the overlying limestone are displayed. It is 8 feet 6 

 inches thick at the fine exposure under the Iron bridge northwest 

 of Cowlesville; 7 feet in the bed of Buffalo creek below Marilla, 

 3 feet 6 inches in a long exposure in the gorge of Cazenovia creek 

 south of Spring Brook. 



GENUNDEWA LIMESTONE 



From Canandaigua lake westward to Lake Erie the black Gen- 

 esee shale is succeeded by a limestone formation consisting at 

 Genundewa point on Canandaigua lake, of several thin layers of 

 limestone and calcareous shale. The layers of limestone decrease 

 in number toward the west, but as the remaining ones retain their 

 peculiar characteristics the formation is easily recognized and is 

 a convenient stratigraphic bench mark. On these quadrangles it 

 consists of a concretionary layer 8 to 10 inches thick overlaid by 

 3 to 6 inches of limestone, slightly shaly and composed, in large 

 proportion, of the minute shells of a pteropod, S t y 1 i o 1 i n a 

 f i s s u r e 1 1 a . This characteristic is persistent, and the formation 

 has been sometimes referred to as the " Styliola limestone " for 

 this reason. Most of the exposures of the Genundewa limestone 

 are in the bottom of ravines where, by its superior hardness over 

 the shales beneath and above, small falls or cascades are produced. 

 It is exposed in both branches of the ravine half a mile west of 

 Alexander ; in the bed of Murder creek on the south side of the 

 Erie Railroad bridge at Griswold ; in the bed of Ellicott creek 1 

 mile west of Darien Center ; above the falls in Durkee creek south- 

 west of Alden ; under the iron bridge northwest of Cowlesville, and 

 in a small ravine half a mile north of the bridge ; finely in the bed of 

 Buffalo creek at Marilla; in the banks of the Buffalo Creek gorge 

 south of the Bullis bridge and in the Cazenovia Creek gorge south 

 of Spring Brook. It dips beneath the water level of Lake Erie 

 a mile southwest of Pike creek. The fauna of the Genundewa 

 limestone in Ontario and Livingston counties comprised 44 species 

 and is of peculiar interest in that the brachiopods and corals so 

 abundant in the Ludlowville and Moscow calcareous layers and 

 shales are absent here, and the fossils are mostly species of cepha- 



