22 NEW YORK STATE MUSEUM 



Tully horizon 



No exposures of the thin lentils of iron pyrites that occur fre- 

 quently at this horizon from Canandaigua westward to Erie county 

 are found on this quadrangle, but a few species characteristic of the 

 Tully limestone occur in the upper layers of the Moscow shale. 



Genesee beds 



Genesee black shale 



As noted before the Genesee black shale is absent here with the 

 possible exception of a few inches of black shale near the eastern 

 border; on the south shore cliffs at North Evans, however, it is again 

 represented by i foot of characteristic shale. 



Genundewah limestone 



The Genundewah limestone is a member of the Genesee shale 

 series in west central and western New York. While the Genesee 

 black shale disappears toward the west from the Genesee river, 

 this limestone intercalation persists to the shore of Lake Erie. 

 It is an irregular stratum of concretionary limestone i to 2 feet 

 thick, extending across the quadrangle and finely exposed on the 

 south branch of Smoke's creek on the south side of the upper railroad 

 bridge at Windom. It continues beyond the quadrangle toward 

 the southwest to a mile south of the mouth of Pike creek where it 

 dips under the water of the lake and toward the east to the vicinity 

 of Seneca lake, having its highest development at Genundewah 

 point on Canandaigua lake. 



Other good exposures besides those at Genundewah point and the 

 ravines toward the north, may be found in the ravine at Bristol 

 Centre and in Mill gull on Honeoye lake in Ontario county; at Eagle 

 point on Conesus lake; on the Genesee river at Mt Morris, Living- 

 ston CO. ; in a small ravine 2 miles north of Wyoming, Wyoming co. 

 and at Griswold station, 6 miles west of Attica. 



In the Genesee valley and Canandaigua lake sections the forma- 

 tion has a thickness of 6 to 8 feet and is composed of several thin 

 nodular or compact limestones separated by black shales. 



The Genundewah limestone is in many places composed almost 

 entirely of the shells of the minute pteropod Styliolina 

 fissurella, and from that fact has been also designated the 

 Styliola limestone. But this peculiar pteropod ooze has also 

 furnished an exceedingly interesting fauna of other forms. Gonia- 



