110 NEW YORK STATE MUSEUM 



black shales may carry with them, and, so far as the main body 

 of the formation is concerned, these variations consist in the 

 appearance now and again of calcareous banks at various alti- 

 tudes from the base of the formation, but more notably predomi- 

 nant toward the lower part of the mass. 



All through the country west of Onondaga county the passage 

 of the black shale upward is so gradual and the diminution of 

 its bituminous matter so almost imperceptible that no division 

 line between the Marcellus and Hamilton deposits is practicable, 

 and no successful attempt has yet been made to delimit the two. 

 Hence naturally a discrepancy appears in the assignments which 

 have been made now and again of the thickness of the Marcellus 

 deposits throughout this region. 



From Onondaga county to Lake Erie the bituminous shales 

 pass upward into and are overlain by a heavy mass of blue and 

 barren shales, shown by the section in the Livonia salt shaft to 

 be fully 200 feet thick, and these carry in regularly diminishing 

 degree the characteristic species of the dark beds below. 



The limestone beds which invite special attention at this occa 

 sion constitute two notable banks, both of which have accepted 

 appellations, one the " Goniatite " or Agoniatites limestone, the 

 other the Stafford limestone. These are persistent over very 

 considerable distances along the strike, one of them curiously 

 enough disappearing from the strata where the other makes its 

 first appearance. The former .{Agoniatite limestone) extends 

 from Schoharie county on the east to about the meridian of 

 Phelps, Ontario co., and the latter from Phelps to Lake Erie. 

 There are at various exposures of the Marcellus shales other 

 more restricted manifestations of calcareous deposits in thin 

 beds which nave afforded some interesting faunal variations, 

 These will be briefly noticed in the following passages. 



Evidence of the two chief limestone banks above noted Avas 

 recorded by the early geologists, the Stafford limestone in the 

 sections given by Prof. Hall 1 , and the Agoniatite limestone in 

 the descriptions by Vanuxem 2 . Though mentioned incidentally 



i Geol. N. Y. 4th geol. (list. 184:3. p. 178, 179, 183. . 

 a Geol. N. Y. 3d geol. dist. 1842. p. 147, 149. 



