1 6 NEW YORK STATE MUSEUM 



contains numerous fossils ; Stromatopora, Halysites, Favosites (diffusely 

 branching form) Spirifer crispus, Trematospira (which is common 

 in the Guelph of Iowa), Coelidium macrospira, Pterinae 

 s u b p 1 a n a. 1 



The association indicates a mixture of Lockport and Guelph species, 

 though there is nothing in it which militates against its construction as a 

 Guelph fauna, as, in fact, a facies of the fauna somewhat removed in space 

 from the reefs about which the true Guelph was centered. We may note 

 that Professor Hall a described and figured specimens from "limestone below 

 the cliff at Niagara Falls" — evidently loose — as Cyrtoceras? su bean- 

 cell a t u m and Gomphoceras? sp. Both are identified with specimens 

 from the Rochester shale but this identification seems erroneous in the for- 

 mer and dubious in the latter case. These fossils are quite distinctly of 

 Guelph habit and it is probable that both were derived from this upper 

 layer. We may properly regard the layer of chert nodules below as pre- 

 senting the first appearance of the Guelph (i. e. the upper) fauna in this 

 section and in this case may conceive the thickness of 45 feet of dolomite 

 above this layer as imperfectly or not at all represented at Shelby. 



The actual measurement of the dolomite section at Niagara Falls is 13 

 feet more than on Oak Orchard creek and this difference is largely if not 

 wholly at the top of the former. It is not now possible to say how much of 

 the section has been planed off in either place or what part of the difference 

 is to be ascribed to the thinning of the formation eastward. That a portion 

 of the top of the section throughout this region is concealed, is indicated by 

 borings. Deep wells in the Niagara region are stated to show about 100 

 feet of limestones above the exposure, 3 but it is altogether uncertain that 

 this is to be accepted as correct or what part of such alleged increase can be 

 ascribed to the dolomite series. 



1 These fossils have been chiefly collected on Goat island by Gilbert van Ingen. 



2 Pal. N. Y. 2: 290, pi. 61. 



^Grabau. N. Y. State Mus. Bui. 45, p. 114. 



