234 POTTSVILLE FAUNA OF OHIO 



Dimensions. The figured specimen measures: height 25 mm., 

 length of hinge line 20 mm., maximum width below hinge line 24 mm. 



Remarks. As stated by Meek this species may be only an extreme 

 variety of P. carbonaria which, according to the figured specimens, show 

 great diversity of form. 1 However, none of these figures, even 2a and 

 2d, which are imperfect in the hinge area, indicate a hinge line as long 

 or as straight or with such angular lateral extremities as P. ? recticar- 

 dinalis. These differences together with the lower, less prominent, and 

 more central beak seem of sufficient importance to justify a distinct 

 species. 



Horizon and locality. Lower Mercer limestone: Licking County, 

 Flint Ridge, Locality 47, r. 



Genus Allerisma King 



Allerisma terminale Hall 

 PL XIII, fig. 15 



1852 Allerisma terminates. Hall, Stani-bury's Exped. to Great Salt Lake, p. 413, 

 PL 2, Figs. 4a, b. 

 Carboniferous: Big Blue River. 



Remarks. Allerisma terminale is another Pennsylvanian species of 

 very wide stratigraphic and geographic distribution which is common 

 and widespread in the Pottsville formation of Ohio above and includ- 

 ing the Lower Mercer limestone. Individuals usually occur in a greatly 

 crushed condition, but are readily recognized by their large size, elon- 

 gate form, and coarse concentric wrinkles. Spinulose surface sculp- 

 ture is characteristic and usually well preserved. 



Horizon and locality. Widely distributed throughout the Lower 

 Mercer and Me Arthur limestones, c. Lower Mercer ore: Jackson 

 County, Locality 56, r. 



Genus Pleurophorella Girty 

 Pleurophorella costata (Meek and Worthen) 



1869 Allorisma costata. Meek and Worthen, Proc. Acad. Nat. Sci. Phil, p. 171. 



Lower Coal Measures: Warren County, Illinois. 

 1873 Allorisma costata. Meek and Worthen, Geol. Surv. 111., Vol. 5, p. 585, PL 20, 



Fig. 15. 



Coal Measures : Warren County, Illinois. 



Description.- This species with its distinctive surface markings 

 is rare in the Pottsville formation of this State and is represented in 

 Meek, F. B., Geol. Surv. 111., Vol. 5, PL 27, Figs. 2a, b, c, d, 1873. 



