1132 



NEW YORK STATE MUSEUM 



Frontenac island 



The best location for the collection of Cobleskill fossils in the 

 vicinity of Union Springs is on Frontenac island in Cayuga lake, 

 about y 2 mile from the village. This island, having an area of 

 one half acre, is the remaining part of the south limb of an anti- 

 cline, which has its axis extending in a direction a little north 

 of east and passing through Hibiscus point, % of a mile north 

 of the island. The upward flexure of the strata at Hibiscus 

 point brings the gypsum beds above the lake level, but the dip on 

 the north side of the anticline makes them again disappear below 

 the lake at a point opposite the railroad junction. 



The surface of the island is nearly level and extends about 6 

 feet above the lake. 



The outcrops of the Cobleskill on the island consist of three 

 strata of hard, dark magnesian limestone, having a dip to the 

 south of about five hundred feet to the mile, thus bringing into 

 view the three layers, which together have a thickness of 8 feet, 

 6 inches. The upper layer, which is soft and quite dark, has a 

 thickness of 3 feet, 2 inches and breaks readily into small angular 

 fragments. With the exception of corals it is the most fossilifer- 

 ous layer. The middle layer which is 2 feet, 10 inches thick, con- 

 tains Stromatopora in abundance and, except that the color is 

 a little darker, it is precisely the same in appearance as the 

 Stromatopora bed of the Manlius limestone, holding a position 

 60 feet higher. The two upper layers are quite uniform in color, 

 which is well retained even after they have been exposed for a 

 considerable length of time. The lower layer, with a thickness 

 of 2 feet, 6 inches, weathers a lighter color than the upper 

 layers, is less fossiliferous and approaches more closely the 

 character of the underlying Eurypterus beds. 



The Cobleskill limestone where exposed on the mainland is also 

 fossiliferous, but no species were found that do not occur on the 

 island. The following list therefore represents secies identified 

 from Frontenac island. 



1 Chaetetes (Monotrypella) arbusculus Hall 



2 Favosites aiagarensis? Hall 



3 Halysites cateaulatns Linn. 



