Geology of Seneca County. 95 



limestone, containing various Zaphrentis, Heliojphylla, etc. ; above 

 it, shales with typical Hamilton fauna. 



2. Keeder's creek, about 1,000 feet from the latter lake, similar, 

 8-10 feet thick, with 5-10 feet of transitional shale beneath, and 

 Marcellus at base of bank. Reliophylhtm Ilalli frequent. Large 

 favosite. A furlong or so up the stream a fall of four or five 

 feet occurs over this rock. 



3. Large hill, K. W. of West Fayette station (MacDougal's 

 P. O.). Here it forms a flat surface on the summit (200 feet above 

 the lake), and an escarpment to the north ; numerous corals are 

 to be found in the field, but there is no direct exposure of the 

 ledge. 



4. Gully of Kendig's creek, one-quarter mile east of MacDou- 

 gal's. The underlying Marcellus well displayed in bed. Steep 

 fall of nearly 15 feet with mill (now run by steam). Large favo- 

 site ; heavy blocks. 



5. Creek, a mile west of Bearytown (Fayette P. O.), Hamilton 

 fauna ; heavy rock, rapids descending 10 feet. 



6. Creek a mile S. E. of Bearytown ; an old mill site. Directly 

 above Marcellus exposures are 12 feet of limy rock breaking in 

 irregular conchoidal masses, large and small, with horizontal 

 tendency. Sparse Hamilton fauna. Heliophyllum Ilalli and 

 another coral. Fall about 10 feet. 



Y. Big Hollow creek, eastern Komulus. Fall of some 30 feet 

 vertically over heavy limestone ledge. Marcellus below down to 

 lake. Hamilton fauna. 



The northern boundary of the Hamilton shales is drawn upon 

 these data. Exposure 3 may be insular ; it is covered with drift 

 to the southward. The Tully limestone lies seven miles to the 

 southward, which is the width of the Hamilton exposure along 

 the plateau. Along Seneca lake, on and quite near the shore, 

 the Hamilton runs 12J miles — from Reeder's creek to the land- 

 ing next south of Lodi Point. 



Tully Limestone. 



This highly developed limestone formation, lying between the 

 shales of the Hamilton and Genesee divisions, acquires great 

 importance as a geological horizon. Its outcrops have, therefore, 

 been studied with care. (See fig. 26.) 



