DESCRIPTION OF SPECIES 225 



Horizon and locality. Lower Mercer member: Perry County, 

 Locality 35, r; Muskingum County, Locality 40, r. McArthur member: 

 Vinton County, Localities 84, 85, r. 



Schizodus subcircularis Herrick 

 PL XII, figs. 14-16 



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

 p. 145, PI. 14, Fig. 18. 

 Coal Measures: Flint Ridge, Ohio. 



Description. 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. How- 

 ever, allowances must be made for the variable character of the Schi- 

 zodus group and for some distortion resulting from compression. The 

 collections studied contain excellent examples from the McArthur 

 member which retain the almost circular form which characterizes the 

 species. The beaks in these specimens are almost median in position. 



Dimensions. A specimen of average size measures: length 14.5 

 mm., height 14 mm., convexity of left valve 4.5 mm. 



Horizon and locality. Harrison ore: Jackson County, Locality 1, 

 r. McArthur member: Jackson County, Locality 80, c; Vinton County, 

 Locality 84, c. 



Schizodus wheeleri Swallow 



1858 Schizodus obscurus. Swallow, Trans. St. Louis Acad. Sci., Vol. 1, p. 193. 



(Non Axinus obscurus Sowerby, 1823.) 



Lower Permian, Kansas. 

 1872 Schizodus wheeleri. Meek, U. S. Geol. Surv. Nebraska, p. 209, PL* 10, Figs. la-f. 



Upper Coal Measures: Missouri, Nebraska, Iowa. 



Remarks. Schizodus wheeleri, with its wide geographic distribu- 

 tion throughout the Pennsylvanian and Lower Permian systems of 

 this country, is present in the middle and upper Pottsville formation 

 of Ohio, above and including the Boggs member. Specimens are 

 often in a good state of preservation and many of them retain, par- 

 tially at least, the fine, regular, concentric surface sculpture of the 

 species. The form is of fairly common occurrence. 



Horizon and locality. Boggs member: Muskingum County, Lo- 

 cality 26 c. Widely distributed in the Lower Mercer, Upper Mercer, 

 McArthur, and Black Flint members, c. 



8 G. B. 25. 



