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NEW YORK STATE MUSEUM 



Guelph fauna ; upper Shelby dolomite 



>- Lockport dolomites 



Guelph fauna ; lower Shelby dolomite 



> Lockport dolomites, largely covered 



Rochester shale 



A significant feature of this occurrence is the double appearance of the 

 Guelph fauna. Its earlier manifestation is after the lapse of 63 feet of 

 Lockport dolomite; it retreated and reappeared after 32 feet more of these 

 Lockport dolomites with their characteristic species, had been deposited. 

 Here it closes the dolomite episode, and the Lockport species have finally 

 withdrawn. We designate these appearances of the fauna as the lower and 

 upper Guelph faunas or, as the local development of the fauna is predi- 

 cable and carries an impress of distinctive nature, as the lower and upper 



