REPORT OF THE STATE PALEONTOLOGIST 1901 433 



Niagara escarpment are so rare, and the cuesta has been so 

 seldom trenched either by natural or artificial means, that till 

 Prof. Arey's discovery, it may be said that we were in almost 

 complete ignorance of its presence. In and about Rochester 

 the fauna seems to have attained a localized development to a 

 profusion not observable elsewhere in the state. During the 

 last year Prof. Arey has, with great consideration, placed his 

 collections of those interesting fossils in the hands of the 

 paleontologist for study. We have found that the material 

 represents a fauna of about 50 species, of which 19 appeared 

 (Niagaran) previously in the same locality, 4 are peculiar to the 

 congeries itself, and 21 are present in common with the typical 

 Guelph fauna of Ontario. It is thus clear that the fauna is not 

 simply a local expression of a late stage of the Lockport dolo- 

 mite fauna, but represents the true Guelph fauna of Ontario. It 

 is possible that the collection we have had in hand does not 

 fully exemplify the fauna, but, as Nellis's quarry is now aban- 

 doned, and there appear to be at present no excavations within 

 the city of Rochester into this formation, we have been at a 

 loss to add to the material already taken out from this region. 

 Field investigations have been made with care for the purpose 

 of tracing this horizon, which, it may be added, is hardly to be 

 separated from the dolomites beneath by lithologic characters, 

 to the west and east of the vicinity of Rochester. The most 

 complete section of the dolomites in the immediate vicinity of 

 the city appears to be that on Aliens creek just to the south, 

 where shaly layers clearly referable to the basal beds of the 

 Salina and chocolate colored dolomites which pertain to the 

 Lockport dolomite series are exposed, but with a covered 

 interval just where one would expect to find the Guelph horizon. 

 In transecting the escarpment at various points between 

 Rochester and Lockport slight traces have been found of the 

 position of this stratigraphic horizon, specially at the exca- 

 vations on the Orchard creek canal feeder south of Shelby, 

 where the abundant nodules of white chert in the compact dolo- 

 mite indicate species of similar character to those at Rochester 

 but in a condition of less satisfactory preservation. 



