DESCRIPTION OF SPECIES 255 



Description. This form resembles very closely the one described 

 by Worthen from the Coal Measures of Illinois as Pleurotomaria illinois- 

 ensis, with the exception that the tubercles at the inner angle of the 

 volutions are somewhat smaller and more irregularly spaced. It also 

 appears identical with the Kentucky form described by Cox as P. 

 depressa. The species is characterized by its low depressed spire and 

 the sharp outer angle of the last volution. The slightly depressed 

 slit-band just above the outer anp-le of the body whorl is distinctly 

 marked. The species has been found only in the Lower Mercer member 

 where it is rare. 



Dimensions. Width 14 mm., height 6 mm., apical angle about 

 125 degrees. 



Horizon and locality. Lower Mercer limestone: Muskingum 

 County, Localities 39, 43, r. 



Genus Schizostoma Bronn 



Schizostoma catilloides (Conrad) 

 PI. XV, figs. 19, 20 



1842 Inachus catilloides. Conrad, Jour. Acad. Nat. Sci. Phil., 1st Ser., Vol. 8, Pt. 2, 

 p. 273, PI. 15, Fig. 3. 

 Carboniferous: Inclined plane of the Allegheny Mountains, Pa. 



Remarks. Schizostoma calilloides is common and widely distrib- 

 uted throughout the Pottsville formation of Ohio. It is present in 

 almost every member in which marine fauna occur from the Harrison 

 ore at the base to the Black Flint at the top. 



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

 a. Sharon ore: Scioto County, Locality 2, c. Lowellville member: 

 Muskingum County, Locality 19, r. Boggs member: .Muskingum 

 County, Locality 26, c. Widely distributed in the Lower Mercer and 

 McArthur members, c. Black Flint member: Jackson County, Lo- 

 cality 87, c; Vinton County, Locality 91, r. 



Genus Naticopsis McCoy 



Naticopsis altonensis (McChesney) 

 PI. XV, fig. 15 



1865 Natica altonensis. McChesney, 111. New Spec. Foss., P. O., PI. 2, Figs. 14 a, b. 



Coal Measures: Alton, Illinois. 

 1868 Naticopsis altonensis. McChesney, Trans. Chicago Acad. Sci., Vol. 1, p. 50, 



PI. 2, Figs. 14a-c. 



Coal Measures: Alton, Illinois. 



