CANANDAIGUA AND NAPLES QUADRANGLES 



9 



replaced by the addition of alumina and carbonate of magnesia, 

 so that the succeeding stratification becomes highly dolomitic. 

 The distinguishing mark of the division as already noted, is the 

 presence of merostonie and phyllocarid crustaceans, which at- 

 tained at this time their culmination of development. 



Along the creek for 10 rods below the bridge at East Victor 

 are from 30 to 40 feet of hard compact dolomites with dis- 

 tinct lines of sedimentation, having a characteristic clink 

 and conchoidal fracture. The dark blue of the rock changes 

 rapidly on exposure to a light, dark or ashen gray. The 

 same horizon appears in the Lehigh Valley Railroad cut 1 mile 

 east of Victor, though the exposure here is for only about 6 feet 

 at the bottom, just over the Camillus shales. Eastward also in 

 the adjoining quadrangle occasional exposures are seen. Remains 

 of the crustaceans referred to are by no means as common here as 

 at the well known localities to the west at Buffalo and to the east 

 in Herkimer county but the horizon is doubtless the same, and 

 segments, heads and appendages of these creatures are not un- 

 common. With them is frequently found a Leperditia, probably 

 L. a 1 1 a Conrad and the brachiopods Whitfieldella 

 1 a e v i s Vanuxem and Leptostrophia varistriata 

 Conrad. 



Cobleskill shale and dolomite 



This is a rather obscure representative of a formation which 

 has recently been shown by the investigations of Hartnagel to ex- 

 tend without interruption from eastern New York to Buffalo and 

 beyond. It is regarded as deposited soon after the close of the 

 period of the Salina and it here consists of dark, hard shale and 

 straticulate, impure limestone, succeeded by a thick bed of mas- 

 sive dolomite, the top of the formation consisting of platten dolo- 

 mites. The thickness ascribed to these beds is approximately 42 

 feet, of which 18 feet are assigned to the shale, 20 feet to the 

 heavy dolomite and 4 feet to the platten dolomite on top. 



The section at East Victor exposes the massive beds of this 

 horizon, immediately below the topmost layers constituting 

 platten dolomite. In the high bluff on the east bank of the creek 



