ber and continues throughout the formation, but occurs most abun- 

 dantly on the Lower Mercer and Black Flint horizons. 



Horizon and locality. Boggs limestone: Rock Cut, Muskingum 

 County (Locality 28), r. Abundant in middle and upper Pottsville 

 formation. 



Genus Rhombopora Meek 

 Rhombopora lepidodendroidea Meek 



1866 Stenopora columnaris (pars). Geinitz, Die Carb. und Dyas in Nebraska, p. 66. 

 (Non Schloth, 1813) 

 Coal Measures: Wyoming and Nebraska. 



1872 Rhombopora lepidodendroides. Meek, U. S. Geol. Surv. Nebraska, p. 141, PL 7, 



Figs. 2a-f . 



Upper Coal Measures: Wyoming, Nebraska, Kansas, Iowa, Missouri, 



Illinois. 



Description. This small, delicate, branching bryozoan with its 

 wide geographic and stratigraphic range in the Pennsylvanian rocks 

 of North America is common in the Pottsville formation of this State 

 above and including the Boggs member. It occurs most abundantly, 

 however, in the Lower Mercer and McArthur limestones. The diam- 

 eter of the largest fragment studied is 2 mm., but the average width 

 varies from 1 to 1.5 mm.. Only one bifurcation was observed on any 

 of the fragments examined, the longest of which measures 18 mm. 



Horizon and locality. Boggs limestone: Blunt Run, Muskingum 

 County (Locality 27), c; Symir.es Creek, Muskingum County (Locality 

 29), c. Common in middle and upper Pottsville formation. 



Class Brachiopoda 



Genus Lingula Bruguiere 



Lingula carbonaria Shumard 



PI. Ill, Figs. 3, 4, 5 



1858 Lingula carbonaria. Shumard, Trans. St. Louis Acad. Sci., Vol. 1, p. 21.". 

 Coal Measures: Clark County, Missouri. 



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



PI. 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 subparallel or slightly rounded ; anterior rrargin sometirres 

 slightly flattened, giving a quadrangular appearance to the shell. 

 Outer covering usually preserved, thin, polished, and marked by fine 

 concentric lines of growth which are crossed by fainter radiating 

 striae, those extending from the beak to the anterior margin being 

 most prominent. 



44 



