GUELPH FAUNA IN THE STATE OF NEW YORK I I 



abundant in the lower part and containing inter alia, Trochoceras 

 desplainense, Orthoceras trusitum, Coelidium macro- 

 spira, Trochonema cf. fatuum, Trematonotus alpheus, 

 Cornulites arcuatus, Poleumita scamnata, P. sulcata, 

 Eotomaria galtensis, Spirifer crispus, Leptaena rhom- 

 boidalis, Pterinea subplana, P. undata, Stromatopora 

 galtensis, Diaphorostoma niagarense, Calymmene niaga- 

 rensis, Proetus sp. This we shall term the upper Guelph bed, and 

 shall have occasion to observe that its fauna is more nearly parallel to that 

 at Rochester than the lower or earlier appearance of the Guelph in this 

 section. 



This is the southernmost exposure on Oak Orchard creek ; and it 

 appears that in the general planing of the country by ice and water any 

 harder beds above would have in some degree at least, resisted erosion and 

 left some trace of themselves in the well channeled way of this stream to 

 the south. 



It seems fair to conclude, therefore, from this section supplemented by 

 similar evidence in Monroe county, that overlying beds, with the possible 

 exception of a few feet of dolomite, were the soft shales and thin " platten " 

 limestones of the Salina, and hence that the upper Guelph horizon, litho- 

 logically, topographically and faunistically here terminates the dolomite 

 period. 



This section is represented in the following diagram. 



