184 POTTSVILLE FAUNA OF OHIO 



P. symmetricus is of rare occurrence, while P. nebraskensis is extremely 

 abundant and widely distributed throughout the Potts ville formation. 

 Horizon and locality. Lower Mercer limestone: Perry County, 

 Somerset, Locality 35, r. Upper Mercer limestone: Holmes County, 

 Salt, Creek Township, Locality 73, r. 



Genus Marginifera Waagen 



Marginifera muricata var. missouriensis Girty 



PL IX, figs. 1-5 



1915 Marginifera muricata var. missouriensis, Girty, Missouri Bureau Geol. and 

 Mines, Vol. XIII, 2nd Ser., p. 350, PL XXX, Figs. 2-5a. 

 Cherokee shale: Missouri. 



Description. Marginifera muricata var. missouriensis is one of the 

 most abundant and widely distributed fossils of the Pottsville forma- 

 tion in Ohio; it occurs in all of the marine limestones with the exception 

 of the Boggs member, and is present in great profusion at some locali- 

 ties in the Lower Mercer limestone. It is small in size and the gibbous 

 ventral valve imparts a globular appearance to the shell. The surface 

 is marked by rather fine, regular costae, crossed by concentric wrinkles 

 which on some specimens reach anteriorly two-thirds the length of the 

 shell; spines are numerous on all parts of the valves. The slight, ill- 

 defined fold near the anterior margin of the ventral valve, mentioned 

 by Girty on the Missouri forms, is absent on specimens from Ohio; 

 this character, however, is not a constant one. 



Dimensions. The measurements of a ventral valve of average 

 size are: length 11 mm., width 13.5 mm., convexity 3.2 mm.; of a dorsal 

 valve: length 10.5 mm., width 12.5 mm., convexity 3.2 mm. 



Horizon and locality. Widely distributed throughout the Lowell- 

 ville, c, Lower Mercer, aa, Upper Mercer, c, McArthur, aa, and Black 

 Flint, c, members. 



Marginifera wabashensis (Norwood and Pratten) 



PL IX, figs. 6-10 



1854 Productus wabashensis. Norwood and Pratten, Acad. Nat. Sci. Phil. Jour., 2nd 



Ser., Vol. 3, p. 13, PL 1, Figs. 6 a-d. 



Ccal Measures: near New Harmony, Indiana. 

 1903 Marginifera wabashensis var. Girty, Prof. Paper. U. S. Geol. Surv., No. 16, 



p. 375, PL 5, Figs. 8, 8a. 



Carboniferous: Colorado. 



Description. This common and characteristic fossil is found 

 everywhere in the marine limestones of the Pottsville formation, al- 



