THE EXPOSURES 349 



The only good natural exposures of the beds comprised within the 

 cuesta are in Skajaquada, Ellicott, and Murder creeks, in Erie county, 

 and at the falls of the Tonawanda or Indian falls, in Genesee county. 

 The contact between the Siluric and Devonic beds is shown in all these 

 exposures. The numerous quarries which are opened in the northern 

 face of the cuesta furnish, however, the best means for the study of the 

 contact and the beds adjoining it. Where the quarries are opened for 

 lime only they seldom penetrate below the Onondaga limestone, but 

 where building stone is quarried or where the Waterlime is the object of 

 search, good sections are usually produced. By far the best of these 

 are in the quarries of the Buffalo Cement Company, in North Buffalo. 

 The old park quarry, the abandoned cement tunnels at Williamsville, 

 and the cement mines at Falkirk and Akron furnish other satisfactory 

 exposures. 



Upper Silurian Rocks of Erie County 

 s a lin a beds 



The Upper Silurian rocks of New York have been divided by Clarke 

 and Schuchert (1899) into the Salina beds, at the base, the Rondout 

 Waterlime, in the middle, and the Manlius limestone, on top. The Sa- 

 lina beds are scarcely exposed in Erie county, the only localities men- 

 tioned by Bishop (1895) being on Grand island and in the bed of Murder 

 creek below the falls at Falkirk. 



RONDOUT WATERLIME 



This name has been resuscitated by Clarke and Schuchert for the 

 hydraulic limestone or Waterlime of New York — that is, the formation 

 characterized by the Eurypterus fauna. This is a very important for- 

 mation in Erie county, being extensively quarried for hydraulic cement. 

 The most satisfactory exposures for purposes of study are in the cement 

 quarries in North Buffalo. Here the stratum quarried for burning is 

 5 feet 8 inches thick (Bishop), and is exposed by the stripping off of the 

 overlying strata. The rock is compact, very fine and evenly grained, 

 and breaks with a conchoidal fracture. The fauna obtained from this 

 stratum comprises, according to Mixer,* 9 species of Eurypterus, 7 of 

 Pterygotus, 2 of Ceratiocaris, a Leperditia, 5 species of Discina (Orbicu- 

 loidea ?), a Lingula, and 2 (?) seaweeds. 



At Akron the cement stratum is 7 feet thick, and at Falkirk, nearby, 

 it ranges from 7} to 8 feet. The total thickness of the Rondout Water- 



* Bishop, 1895, p. 340. 



