8 NEW YORK STATE MUSEUM 



The proportion of calcareous and argillaceous matter varies 

 considerably in different layers, the composition of some of them 

 being such as to make true hydraulic limestone or natural cement 

 rock. A bed of this character at the top of the formation and 

 about 6 feet thick has been quarried extensively at Buffalo, 

 Williamsville and Akron for the production of natural cement, 

 and other layers were formerly utilized for this purpose in the 

 central part of the State. 



This formation receives its name from its favorable exposure in 

 the township of Bertie, Ontario. It may be seen to excellent 

 advantage at the falls of EUicott creek in the village of Williams- 

 ville and there are frequent small exposures of the upper beds all 

 along the lower part of the escarpment to Clarence and the large 

 quarry two and one-half miles farther east. 



Fossils are rare in the Bertie limestone here except the ostracod, 

 Leperditia scalaris Jones, and the small brachiopod 

 Whitfieldell'a laevis (Whitfield) : these two occurring in 

 considerable numbers in several thin layers and occasionally in the 

 more compact and thicker layers. The stratum of cement rock at 

 the top of the formation contains the remains of a peculiarly inter- 

 esting arachnid or eurypterid fauna, which has recently been fully 

 discussed and illustrated by Clarke and Ruedemann (N. Y. State 

 Mus. Mem. 14, 1912). The wealth of this formation in these 

 fossils has made it widely known and of great interest to 

 paleontologists. 



COBLESKILL WATERLIME 



West of the Genesee river the Bertie waterline is succeeded by 

 a few feet, not more than 6 to 8 on the Depew quadrangle, or dark 

 subcrystalline dolomitic limestone in uneven layers, usually not 

 more than a few inches thick, separated by thin seams of black 

 carbonaceous matter. After exposure this rock sometimes has a 

 brecciated appearance and is usually more or less porous owing to 

 the removal by dissolution of crystals of calcite and of a small 

 coral, C y a t h o p h y 1 1 u m h y d r a u 1 i c u m Simpson, which 

 occurs quite abundantly here and in the Buff'alo quadrangle, but is 

 very rare or absent from the Cobleskill in the central part of the 

 State. The rock resembles the Bertie in being very dark when 

 freshly quarried but weathering to a light gray or buff color. It 

 is known to quarrymen as the '' bull head " or " pumpkin head," 

 and is of considerable economic value, being used largely in Buffalo 

 for foundation walls and similar purposes. 



