1887 Macrodon carbonaria. Herrick, Bull. Den. Univ., Vol. 2, p. 32, PI. 4, Figs. 21, 

 14. 

 Coal Measures: Flint Ridge, Ohio. 



This species is particularly abundant in the Lower Mercer lime- 

 stone although it has been found as low as the Boggs; it is common 

 also in the higher members. It is characterized by surface sculpture 

 of prominent, regular, radiating plications which become considerably 

 larger and stronger on the flattened posterior portion below the hinge 

 line. The dimensions of a specimen of representative size from the 

 Boggs member are: length 20 mm., height from beak to opposite 

 margin 9 mm. 



Horizon and locality. Boggs limestone: near Hopewell P.O., 

 Muskingum County (Locality 26), c. Common and widely distributed 

 in members above the Boggs. 



Parallelodon obsoletus (Meek) 



1871 Macrodon obsoletus. Meek, Rep. Regents Univ. W. Va. 



Lower Coal Measures: Monongahela County, West Virginia. 

 1875 Macrodon obsoletus. Meek, Pal. Ohio, Vol. II, p. 334, PI. 19, Fig. 9. 



Coal Measures: Newark, Ohio. 



This species of Parallelodon appears in the Lowellville limestone 

 but is most characteristic and abundant in the Lower Mercer lime- 

 stone. It is distinguished from the other species of Parallelodon occur- 

 ring in this State by the apparent absence of all surface markings. 

 The obscure, fine, radiating lines of the posterior-dorsal region, referred 

 to by Meek 1 do not appear on the specimens examined. The indi- 

 viduals from the Lowellville limestone are all imperfectly preserved, 

 so that their identification is not accompanied by a great degree of 

 certainty. A specimen of average size from the Lower Mercer lime- 

 stone measures: length 27.5 mm., maximum height 11.5 mm., convexity 

 of right valve 5.5 mm. 



Horizon and locality. Lowellville limestone: Hopewell P.O., 

 Muskingum County (Locality 19), r. Common in the Lower Mercer 

 limestone. 



Parallelodon tenuistriatus (Meek and Worthen) 



1866 Area striata. Geinitz, Garb, und Dyas in Nebraska, p. 20, tab. 1, Fig. 32. 



(Not Mytilites striatus Schloth, 1817), Nebraska City, Nebraska. 



1867 Macrodon tenuistriata. Meek and Worthen, Proceed. Chicago Acad. Sci., 



Vol. 1, p. 17. 



Upper Coal Measures: Springfield, Illinois. 



Parallelodon tenuistriatus is a common fossil throughout the 

 Pottsville formation of this State, but occurs in especial abundance 

 in the Harrison ore and the Lower Mercer and Me Arthur limestones. 

 The forms from the Harrison ore and McArthur limestone are un- 

 usually small and diminutive, while in the Lower Mercer and other 



iMeek, F. B., Pal. Ohio, Vol. II, p. 334, 1875. 



69 



