GUELPH FAUNA IN THE STATE OF NEW YORK 



113 



In the lower Shelby horizon the cephalopods prevail, notably in species 

 and profusely in individuals ; furthermore of the three brachiopods one is 

 Monomorella noveboracum which extraordinarily abounds and is 

 nowhere else seen ; of the four gastropods Trematonotus alpheus 

 is amazingly prolific and Poleumita crenulata is very common. As 

 to the corals we have every reason for believing that, originally abundant, 

 their skeletons have been largely destroyed by diagenesis. 



In the upper Shelby-Rochester horizon, there has been less destruc- 

 tion of the corals, and the gastropods and cephalopods are prevailing 

 species though not rising to such individual development as in the 

 earlier appearance. 



Comparing this condition with the relative development of these 

 classes in the typical Guelph fauna of Ontario as given by Dr Whiteaves 

 we find a corresponding prevalence of gastropods and cephalopods ; the 

 lamellibranchs are few in species (nine in a total fauna of 133 species) but 

 one of these is the ponderous Megalomus canadensis which is 

 extraordinarily abundant at definite horizons. The brachiopod species rise 

 to 24 but it is a noteworthy fact that throughout this fuller representation 

 of the Guelph fauna there is a larger percentage of normal or slightly 

 modified Niagaran forms than is present in the New York Guelph. No 

 crinoids or bryozoans are present in either case. 



