542 CHARLES S. PROSSER 



Osgood beds of Indiana;" and apparently refers the Dayton 

 limestone, Orton 1870, which occurs at the base of the shale, to 

 the same division.' He also stated that "the West Union cliff 

 may correspond to the limestone courses in the upper part of the 

 Osgood beds in Indiana and western Kentucky, but it has so far 

 not been sufificiently investigated to admit of correlation. "(^) 



24. The Canadian Survey has shown that the Medina for- 

 mation may be traced by surface outcrops from Niagara River 

 across Ontario and along the western shore of Georgian Bay. 3 

 Later the red rocks penetrated in deep wells in southern Onta- 

 rio, '^ the Lower Peninsula of Michigan, s and Ohio ^ have 

 been referred to the Medina formation. Dr. Lane, however, 

 stated that in Michigan the Medina shale, "both lithologically 

 and in the driller's records, is quite as likely to go with those 

 below it. It is really a transition bed."'' There is evidently 

 uncertainty regarding the age of the red shales penetrated in the 

 oil and gas wells of northwestern Ohio ; but, in the absence of 

 positive knowledge, they are left provisionally in the Upper 

 Silurian and called Medina with a query. 



25. There is a question whether the Belfast bed is of suffi- 

 cient importance to be given the rank of a formation. 



26. At present whether the line of separation between the 

 Upper and Lower Silurian should be drawn at the top or bottom 

 of the Belfast bed is a matter of uncertainty. Dr. Foerste states : 

 " I am not certain as to the age of the Belfast bed myself; " and 

 he also says that "it is the only bed which may be Lower Silu- 

 rian and which may be of Medina age." ^ And in an earlier 

 paper Dr. Foerste stated that 



^ Ind. Dept. Geol. and Nat. Res., Twenty-fourth Ann. Rept. (1900), pp. 44, 80. 



-Ibid., p. 80. 



3 Geol. Surv. Canada, Rept. Prog, from Commencement to 1863, 1863, pp. 312- 

 21; and also see Atlas, Geol. Map of Canada, 1864. 



■*Brumell, ibid., Ann. Rept., N. S., Vol. V, Part II (1892), pp. 52 ff. 



5 Lane, Geol. Surv. Mich., Vol. V, Part II (1895), ?• 3° and plates. 



^ Orton, Rept. Geol. Surv. Ohio, Vol. VI (1888), pp. 11 £f., as well as in later 

 reports of the Ohio Survey. 



7 Geol. Surv. Mich., Vol. V, Part II, p. 30. 



^Ind. Dept. Geol. and Nat. Res., Twenty-fourth Ann. Rept. (1900), p. 68. 



