County (Locality 20), c; Symmes Ford, Muskingum County (Locality 

 21), c; Lowellville, Mahoning County (Locality 22), a. Boggs lime- 

 stone: near Hopewell P. 0., Muskingum County (Locality 26), a; 

 Blunt Run, Muskingum County (Locality 27), a; Rock Cut, Muskin- 

 gum County (Locality 28), c; Symmes Creek, Muskingum County 

 (Locality 29), c. 



Chonetes mesolobus Norwood and Pratten 

 Pi. Ill, Figs. 9, 10. 



1855 Chonetes mesoloba. Norwood and Pratten, Jour. Acad. Nat. Sci. Phil. 2nd 

 Ser., Vol. 3, p. 27, PI. 2, Figs. 7a-c. 

 Coal Measures: Bellville, Illinois; Charboniere, Missouri. 



This common and characteristic fossil of wide distribution through- 

 out the Pennsylvanian rocks of the United States, is rarely found in the 

 lower Pottsville formation of Ohio, but is commonly and universally 

 distributed in the members including and above the Lower Mercer 

 limestone. It is, however, particularly characteristic of the Lower 

 Mercer horizon in which it occurs in extreme abundance. C. choteau- 

 ensis characterizes the Lowellville and Boggs members, while C. 

 mesolobus has not been found on either horizon, with the exception 

 of a few individuals from the Boggs limestone at a single locality. 

 The former species seems to have disappeared almost entirely from 

 the Pottsville sea by the advent of Lower Mercer time, for it has 

 been discovered only in the Lower Mercer of Scioto County where 

 it is of very rare occurrence. In its place C. mesolobus appears and is 

 abundant and wide-spread, persisting throughout the remainder 

 of the Pottsville and the Allegheny formations. 



Horizon and locality. Boggs limestone: Blunt Run, Muskingum 

 County (Locality 27), r. Abundant and universally distributed 

 throughout the Lower Mercer and upper Pottsville formation. 



Genus Productus Sowerby 

 Productus cora d'Orbigny 



1857 Productus cora. De Koninck, Monog. du Gen. Prod, et Chon., p. 50, PI. 4, 

 Figs. 4a, b; PI. 5, Figs. 2a-d. 



Carboniferous: Guernsey County, Flint Ridge, and Zanesville, Ohio; 

 Indiana, Nova Scotia, Bolivia, etc., South America. 



Description. This species is a common one in the marine lime- 

 stones of the Pottsville formation, but does not become abundant 

 below the Lower Mercer member. Although it varies much in size, 

 it is generally large, a representative specimen from the Lower Mercer 

 limestone having the folio wing measurements: length 47 + mm., length 

 of hinge line 40 mm., width 50 -f- mm. The hinge line is commonly 

 shorter than the greatest width of the valves, which are marked with 

 fine, sinuous lines. Coarse, concentric wrinkles cover the visceral 

 regions, but become still more deeply impressed on the ears. The 



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