10 



NEW YORK STATE MUSEUM 



was referred by Bishop to the "Onondaga limestone" (in distinction 

 from the Corniferous limestone, which in this paper is termed 

 Onondaga limestone) and to the Manlius limestone by Clarke 1 and 

 Grabau. 2 



The Cobleskill waterlime immediately overlies the cement layer, 

 the transition being gradual through 2 or 3 feet of strata, above 

 which the rock is a dark subciystalline dolomitic limestone in 

 uneven layers, usually but a few inches thick, separated by thin 

 seams of carbonaceous matter. It sometimes has a brecciated 

 appearance and after exposure is usually more or less porous, 

 owing to the dissolving out of calcite crystals and of a small coral 

 Cyathophyllum hydraulicum, which is very com- 

 mon throughout and specially so in the upper part. Though very 

 dark colored when fresh, the rock becomes buff or light brown 

 when exposed and it is locally known to quarrymen as "bullhead" 

 or "pumpkin head." 



The formation is 7 to 9 feet in thickness on this quadrangle, the 

 variation being due to erosion of the upper surface and not to 

 irregularity of deposition which the evenness of the bedding planes 

 shows to have taken place in quiet waters. 



At Falkirk, Erie co. this formation attains a thickness of 14 

 feet, but it becomes thinner again toward the east as far as Livings- 

 ton county; then it increases slowly to 10 feet in Herkimer county, 

 again diminishing to 6 to 8 feet in the Hudson valley. The rock 

 is fairly fossiliferous, the most abundant form being the small 

 coral Cyathophyllum hydraulicum Simpson. 



Besides this are found in Erie county: 



Nematophytum crassum Penhallow 

 Favosites sp. 



Orthothetes interstriatus Hall (=0. 



hydraulicus Whitfield) 

 Spirifer eriensis Grabau 

 Whitfield ella sulcata Vanuxem 



W. nucleolata Hall var. 

 W. cf. laevis Whitfield 

 Rhynchonella sp. 

 Loxonema ? 

 Pleurotomaria ? 

 Trochoceras gebhardi Hall 



There are good exposures of this formation on Scajaquada creek 

 in Forest Lawn cemetery; in the Buffalo Cement Co.'s quarries; 

 in Miller's quarry and at Williamsville on this quadrangle, and at 

 Akron, Falkirk, Indian Falls, Morganville, North Leroy, East 

 Victor, Union Springs, DeWitt, Cobleskill, Rondout and many 

 other places in the central and eastern parts of the State. 



1 N. Y. State Mus. Mem. 3. 1900. 

 -'Geol. Soc. Am. Bui. 1900. v. 11. 



