^r 



134 



NEW YORK STATE MUSEUM 



the Cedarville dolomite shows an exposure of 23 feet, with a total of 40 



feet. In connection with this section it is remarked : ' 



It has received the names of various localities where it is distinctly 

 shown, being styled the Guelph formation in Canada, the Racine beds or 

 Milwaukee beds in Wisconsin and the Bridgeport beds in northern Illinois. 

 In southern Ohio no local name can be selected as appropriate and free 

 from ambiguity as the Cedarville limestone. 



Finally in regard to this formation generally within the state of Ohio, 



Dr Orton wrote in 1893 : 2 



The uppermost division of the [Niagaran] formation is the Guelph 

 limestone which differs very noticeably in several points from the Niagara 

 limestone proper. . . It has a maximum thickness in southern Ohio of 

 200 feet. . . It is either massive or very thin bedded. It is porous to an 

 unusual extent. It is generally very light in color. It is exceedingly rich 

 in fossils containing a large number that is thoroughly characteristic. 



Unlike the previously named divisions of the Niagara, the Guelph 

 limestone is as well developed in northern as in southern Ohio in all 

 respects. Not more than 40 feet of it are found in its outcrops there, but 

 the drill has shown several times this amount of Niagara limestone, without 

 giving us, however, the data needed for referring the beds traversed to their 

 proper subdivisions. What facts there are seem to point to the Guelph as 

 the main element in this underground development of this formation in this 

 portion of the state. 



From the foregoing we may conclude that the area in which the 

 Guelph fauna manifests itself extends from Wayne county, N. Y. westward 

 to Hamilton Ont, thence northwestward to Cape Hurd and Manitoulin 

 island, and northward almost to James bay. Here it follows the Niagaran 

 on the inner side of the vast arc spanned by that formation over the islands 

 of Georgian bay, the north shore of Lake Huron and north and west 

 shores of Lake Michigan. Still farther to the northwest, evidence of this 

 sediment is afforded by the presence of the coral Pycnostylus guel- 

 ph en sis and the Stromatoporoid C la t h ro t d i c ty u m ostiolatum, 

 on the west shore of Lake Manitoba. 3 



1 Geol. Ohio. 1874. 2:674. 



2 Geol. Ohio, 7: 12. 



3 Reported by Whiteaves. Paleozoic Fossils. 1893. v. 3, pt 2, p. 46. 



