166 POTTSVILLE FAUNA OF OHIO 



not rounded typically, but are more or less accurately truncated, some- 

 times even slightly concave, the serrations decrease in prominence with 

 the size of the specimens; the indentations are bordered by crescentic 

 non-poriferous spaces; these spaces are large and conspicuous in the 

 large forms, decreasing to narrow, but distinct proportions in the smaller 

 specimens." The zooecia are small and regular although not close in 

 their arrangement. 



The form is common and widely distributed in the middle and 

 upper Potts ville formation, but is especially numerous and character- 

 istic in the Lower and Upper Mercer and Black Flint members. It has 

 not been recorded from any of the higher Pennsylvanian formations of 

 this State. 



Horizon and locality. Lower Mercer member: widely distributed, 

 c. Upper Mercer member: Muskingum County, Localities 29, 43, 

 68, c; Coshocton County, Locality 70, c. McArthur member: Hocking 

 County, Locality 86, c. Black Flint member: widely distributed, c. 



Class Brachiopoda 

 Genus Lingula Bruguiere 



Lingula carbonaria Shumard 

 PI. VII, figs. 1-3 



1858 Lingula carbonaria. Shumard, Trans. St. Louis Acad. Sci., Vol. 1, p. 215. 



Coal Measures: Clark County, Missouri. 

 1873 Lingula mytiloides ? Meek and Worthen, Geol. Surv. 111., Vol. 5, p. 572, PL 25, 



Fig. 2. 



Coal Measures: Illinois. 



Description. Shell varying in size from small to almost medium; 

 subquadrangular-ovate in outline; ratio of length to width about 3:5. 

 Beak minute, elevated; umbonal region and middle portion of valves 

 moderately convex, becoming flattened toward the sides and front; 

 posterior margin somewhat pointed, curving regularly into the sides, 

 which are sub parallel or slightly rounded; anterior margin sometimes 

 slightly flattened, giving a quadrangular appearance to the shell. Outer 

 covering usually preserved, thin, polished, and marked by fine con- 

 centric lines of growth which are crossed by fainter radiating striae, 

 those extending from the beak to the anterior margin being most promi- 

 nent. 



Dimensions. The ,great variation in the size of the species can be 

 noted by the following measurements: a specimen of large size from the 

 Upper Mercer member, length 12 mm., width 8 mm.; a large specimen 

 from the Anthony coal horizon, length 11 mm., width 6.7 mm., a small 



