170 POTTSVILLE FAUNA OF OHIO 



Dimensions. The measurements of the two most perfect speci- 

 mens obtained are respectively: length 22 + mm., 25 + mm.; maximum 

 width 18 mm., 20 mm. 



Remarks. Another Pennsylvanian species which is closely related 

 to the Pottsville form from Ohio was originally described by Meek as 

 Lingula scotica var. nebraskensis and later by Girty as Lingulipora 

 nebraskensis, which can be distinguished from our form by its much 

 smaller size and fewer concentric lirae. Lingulipora nebraskensis as 

 described by Girty is also a broader form with the length and width 

 of the shell approximately equal; however this character may not be 

 of specific importance inasmuch as Herrick's typical G. waverlyensis 

 has similar proportions. Generically, our form is assigned to Glossina 

 on account of its characteristic cuneate shape, rather than to Lingulipora, 

 as the punctate structure which characterized the latter genus is by no 

 means definitely established on our shell. It is of rare occurrence in 

 rocks of Pennsylvanian age and has been found only from the Lower 

 Mercer limestone. 



Horizon and locality. Lower Mercer limestone: Muskingum 

 County, Locality 43', r; Licking County, Flint Ridge, Locality 49, r. 



Genus Orbiculoidea d'Orbigny 

 Orbiculoidea capuliformis (McChesney) 



1860 Discina capuliforma. McChesney, Desc. New Pal. Fossils, p. 72. 



1861 Discina capuliformis. McChesney, Trans. Chicago Acad. Sci., Vol. 1, p. 23, PL 2, 



Fig. 20. 



Coal Measures: Springfield, Illinois; 12 miles nw. of Springfield, Missouri. 



Description. Specimens of an Orbiculoidea are abundant in the 

 black bone shale on the Sharon ore horizon and have been referred 

 with some doubt to Orbiculoidea capuliformis. They show consider- 

 able variation in size, ranging from those 6 mm. in diameter to forms 

 which are relatively large; the outline of both valves is circular. The 

 beak of the dorsal valve is slightly posterior to the center; as the speci- 

 mens are greatly flattened, it is possible only to make conjectures con- 

 cerning the convexity, which seems to have been moderate. The 

 ventral valve is also compressed, some specimens showing a slightly 

 convex region surrounding the almost centrally located beak, the valve 

 becoming concave toward the margins; a deep, broad slit extends from 

 the beak posteriorly to a point about two-thirds the distance from 

 the beak to the margin; slit widest in the central portion. The sur- 

 face is marked by numerous fine, concentric striae which are regularly 

 arranged; on a few forms very faint radiating markings are visible. 

 Crushed specimens from the Harrison ore, similar to those just de- 

 scribed, have been referred tentatively to the same species, while more 



