DISPLAY OF CHAZY ON VALCOUR ISLAND. 295 



in thickness — in fact the whole formation, excepting the uppermost 80 feet 

 and an interval of 200 feet covered by soil. The 80 feet here lacking are 

 found at the northern end of the island underlying the Black Kiver, and 

 the concealed 200 feet are well displayed on the shores of the mainland to- 

 ward the west and in the vicinity of the railway station recently built to 

 accommodate the new Hotel Champlain at Bluff Point. 



The strata of the Valcour section are as follows, in ascending order : 



Group A (Lower Cliazy). 



Thickness. 



1. Gray or drab-colored sandstone, interstratified with thin (or 



sometimes thick) layers of slate, and with occasional thin 

 layers of limestone at the base, containing Camerella (?) cos- 

 tata, Bill . . . . . . . 56 feet. 



The slaty sandstone gradually passes into 



2. Massive beds, made up of thin alternating layers of tough slate 



and of nodular limestone, containing undetermined species 



of Orthis and Orthoceras . . . . .82 feet. 



3. Dark bluish-gray, somewhat impure limestone, in beds of vari- 



able thickness ; often packed with Orthis costalis, Hall, 

 which occurs with more or less frequency through the whole 

 mass. Other fossils are : Lingula kuronensis. Bill. ; Harpes 

 antiguatus, Bill.; Harpes ottawaensis, Bill. (?) ; Illcenus 

 ardurus, Hall (=1. Bayfieldii, Bill.); Litiiites, sp. (?) . 110 feet. 



4. Gray, tolerably pure limestone in beds 8 to 20 inches thick 



separated by earth}^ seams, the bedding being uneven. 

 Many layers consist of crinoidal fragments, largely of Palce- 

 ocystites tenuiradiatus, Hall, ^ear the middle of the mass, 

 for a thickness of 10 feet, some of the fragments and small 

 ovoid masses (Bolboporites americanus, Bill.) are of a bright 

 red color ; and these beds on the west side of Bluff Point are 

 extensively quarried and furnish a fine marble for in-door 

 use . . . . . . . .90 feet. 



Making for the total thickness of J. . . . 338 feet. 



Group B (^Middle Chazy). 



1. Impure, nodular limestone, containing Maelurea magna, Leseuer. 25 feet. 



2. Gray, massive, pure limestone, abounding in crinoidal frag- 



ments . . . . . . .20 feet. 



3. Bluish-black, thick-bedded limestone, usually weathering so as 



to show pure nodular masses enveloped in a somewhat im- 

 pure, lighter-colored matrix ; everywhere characterized by 

 Maelurea magna. Near the middle of this mass, for a thick- 

 ness of about 30 feet, the fossils are silicified and of jet-black 

 color. The more important, besides Maelurea, are species of 

 Strophomena, Orthis and Orthoceras . . . .210 feet. 



