DESCRIPTION OF SPECIES 163 



Septopora biserialis var. gracilis (Meek) 



1875 Synocladia biserialis (gracilis, suggested). Meek, Pal. Ohio, Vol. II, p. 326, PL 



20, Figs. 5a, b. 



Lower Coal Measures: Near Newark, Ohio. 

 1887 Septopora biserialis var. gracilis. Foerste, Bull. Den. Univ., Vol. 2, p. 80, PL 7, 



Figs. 7a-c. 

 Coal Measures: Flint Ridge, Ohio. 



Description. This variety of Septopora biserialis occurs through- 

 out the middle and upper Pottsville formation of this State. It can be 

 distinguished from typical S. biserialis by its more slender branches, 

 by the more regular arrangement of the dimorphic cells on the non- 

 poriferous side, one cell being located at the union of each dissepiment 

 with the branches, and by the presence of a faintly developed median 

 ridge on the non-poriferous side. As the representatives of the species 

 are often found in a poorly preserved condition, it is not always possible 

 to distinguish the variety gracilis, which is probably much more com- 

 mon in occurrence than is indicated in the list of localities below. 



Horizon and locality. Lower Mercer limestone: Scioto County, 

 Locality 31, r; Muskingum County, Localities 27, 43, 45, c; Licking 

 County, Localities 46, 48, 49, c; Mahoning County, Locality 53, r. 

 Upper Mercer member: Muskingum County, Locality 68, r; Coshocton 

 County, Locality 70, r. Black Flint member: Vinton County, Lo- 

 cality 91, r. 



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 lepidendroides. 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: Muskingum County, 



