408 GEOLOGY OF OHIO. 



fore made some remarks upon them, preceding their descriptions, more 

 extended than would be convenient in this place. 



The species illustrated on Plate VIII are from the Huron and Erie 

 Shales with one exception {Aristozoe canadensis), and the remarks pre- 

 ceding their description will sufficiently explain their grouping. 



Those illustrated on the two following Plates, Nos. IX and X, are 

 all from the limestone layers known as the Maxville limestones, and al- 

 though several are of previously undescribed species, enough of them 

 are recognized forms to fully establish their geological horizon, which 

 appears to be equivalent to the St. L,ouis and Chester beds of Illinois 

 and the surrounding States. This conclusion, I believe, had been 

 reached by Mr. F. B. Meek during his work on the Ohio fossils, at least 

 his labels on some specimens of Spirifera contracta in the State Cabinet 

 at Columbus would indicate this conclusion. The possibility of full}' 

 and satisfactorily identif} r ing any of the divisions of the L,ower Car- 

 bonifereous formations of the more western States among the beds 

 represented beneath the true Coal Measures of Ohio, must certainly be 

 considered as an advantage in the study of these formations. Not only 

 is this true from a stratigraphical point of view as enabling us to 

 identify a stratum or formation over a much greater extent of country 

 and thereby trace out and locate its history in time; but also palaeonto- 

 logically, as enabling us to satisfactorily identify many of the slightly 

 varying forms of fossils represented in these beds with those from other 

 localities, instead of having them described as distinct species, founded 

 upon minute or imaginary differences resulting principally from a 

 change in the state of preservation or of the conditions of life under 

 which they may have existed during the deposition of the sediments 

 in which they are now found. There seems to be a constantly growing 

 tendency to describe as new species forms which vary in the slightest 

 particular from the established species, and it often arises from the in- 

 abilitj^ to satisfactorily identify the beds in which they are found with 

 those from other localities where the stratigraphical relations are already 

 known, and I cannot but regret that it is not practicable to work out 

 the fossils of other of the Ohio formations, as I am fu'ly persuaded 

 there are several of these which could be positively identified with well- 

 known formations in other States, were this done. This is shown by 

 the fossils from the red Iron-stone beds of the Waverly at Sciotoville, 

 Ohio, among which are forms which indicate the Burlington or Burling- 

 ton and Keokuk beds of Iowa and Illinois. On Plate X, fig. 4 a-c, of 

 Vol. II, Pal. Ohio, is represented a Productus in the condition of an in- 

 ternal cast, which when studied in numbers in connection with Pro- 

 ductus flemingi var. burlingtonensis Hall; from Burlington, Iowa, and 

 Ouincy, Illinois, cannot fail to be identified as the same species, while 

 the Hemipronites crenistria of the same plate scarcely differs from Ort/iis 

 keokuk of the same beds ; and on Plate XIV of the same volume, fig. 6, 



