DESCRIPTION OF SPECIES 185 



though it is especially abundant in the Lower Mercer and Me Arthur 

 members. It is generally found in an excellent state of preservation. 

 The ventral valve is very gibbous or even globular, having the greatest 

 curvature in the posterior third of the shell. The hinge line is ex- 

 tended forming the greatest width of the valve; the beak is small, 

 depressed, and slightly incurved, while the visceral region is flattened. 

 The valve is divided into two prominent lobes by a deep, narrow sinus, 

 and the entire surface is covered .with fine, often obscure, radiating 

 striae, with small, indistinct concentric wrinkles covering the visceral 

 region and ears; a few spines are scattered over the surface, two of 

 which are generally located near the center of the valve, one on either 

 side of the sinus. 



Dimensions. Length 12.7 mm., length of hinge line 14 mm., 

 greatest width of valve below hinge line 13.5 mm., convexity 9 mm. 



Remarks. Marginifera wabashensis is the common Pennsylvanian 

 fossil which has been described and figured in various Ohio reports as 

 Productus longispinus. 1 It likewise agrees very closely with the genicu- 

 late forms from Colorado described and figured by Girty as M. wabash- 

 ensis var. 2 



Horizon and locality. Lowellville limestone: Muskingum County, 

 Locality 20, r; Mahoning County, Locality 22, r. Widely distributed 

 throughout the Boggs, Lower Mercer, Upper Mercer, McArthur, and 

 Black Flint members, aa. 



Genus Dielasma King 

 Dielasma bovidens Morton? 



1836 Terebratuld bovidens. Morton," Am. Jour. Sci., 1st Ser., Vol. 29, p. 150, PI. 2, 

 Fig. 4. 

 Coal Measures: Ohio Valley. 



Remarks. A few specimens of a small brachiopod apparently 

 closely resembling Dielasma bovidens were obtained from the Lower 

 Mercer limestone on Flint Ridge. Their condition of preservation, 

 however, is too poor to permit the identification to be made with much 

 confidence, especially as no other specimens were found elsewhere in 

 the Potts ville formation of this State. 



Horizon and locality. Lower Mercer limestone: Licking County, 

 Flint Ridge, Locality 47, r. 



derrick, C. L., Bull. Den. Univ., Vol. 2, p. 48, PI. 2, Figs. 25, 27, 28, 1887. 

 Mark, C. G., Bull. Den. Univ., Vol. XVI, PL 8, Fig. 7, 1911. 

 Mark, C. G., Geol. Surv. Ohio, Fourth Ser., Bull. 17, p. 302, PI. 13, Fig. 8, 1912. 

 2 Girty, G. H., U. S. Geol. Surv., Prof. Paper No. 16, p. 385, PI. 5, Figs. 8, 8a, 1903. 



