Dimensions. A specimen from the Boggs limestone measures: 

 length about 70 mm., height 56.5 mm., thickness of left valve 14 

 mm. (somewhat crushed). 



Horizon and locality. Boggs limestone: near Hopewell P.O., 

 Muskingum County (Locality 26), r. Also present in the Lower 

 Mercer limestone, r. 



Schizodus affinis Herrick 



1887 Schizodus affinis. Herrick, Bull. Den. Univ., Vol. 2, p. 41 , PI. 4, Figs. 22, 22a. 

 Coal Measures: Flint Ridge, Ohio. 



Schizodus affinis is a common fossil of wide stratigraphic range 

 in the Pottsville rocks of this State; it is found from the Harrison ore 

 at the base to Me Arthur member near the top. The species exhibits 

 considerable variation in size. A individual of average size from the 

 Harrison ore measures: length 17.5 mm., height 14.2 mm., thickness 

 of left valve 4.8 mm. 



Horizon and locality. Harrison ore: Jackson County (Locality 

 1), r. Boggs limestone: near Hopewell P.O., Muskingum County 

 (Locality 26), c; Rock Cut, Muskingum County (Locality 28) c. 

 Also common in the Lower Mercer and McArthur limestones. 



Schizodus curtus Meek and Worthen 



1866 Schizodus curtus. Meek and Worthen, Proc. Chicago Acad. Sci., Vol. 1, p. 18. 

 1887 Schizodus curtus. Herrick, Bull. Den. Univ., Vol. 12, pp. 42, 145, PI. 14, 



Fig. 20. 



Coal Measures: Flint Ridge, Ohio. 



This small species of Schizodus appears in the Boggs member, 

 but is of relatively rare occurrence except in the Lower Mercer and 

 McArthur limestones. 



Horizon and locality. Boggs limestone: near Hopewell P.O., 

 Muskingum County (Locality 26), r; Blunt Run, Muskingum County 

 (Locality 27), r. Present in fossiliferous horizons above the Boggs 

 member. 



Schizodus subcircularis Herrick 



1887 Schizodus subcircularis. Herrick, Bull. Den. Univ., Vol. 2, p. 41, PI. 4, Fig. 24; 

 p. 145, PL 14, Fig. 18. 

 Coal Measures: Flint Ridge, Ohio. 



A single, well preserved individual of Schizodus from the Harrison 

 ore has been referred to this species, the form of which is slightly 

 more elongate than Herrick's figured specimens indicate. However, 

 alowances must be made for the variable character of the Schizodus 

 group and for some distortion resulting from compression. The 

 collections studied contain excellent examples from the Lower Mercer 

 and McArthur members which retain the almost circular form which 

 characterizes the species. The beaks in these specimens are almost 



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