3 88 



NORTH AMERICAN INDEX FOSSILS. 



XIX. Edmondia de Koninck. 

 Oval or subcircular, gaping anteriorly. A narrow ridge present 

 behind the beaks. Beaks varying from subcentral to nearly an- 

 terior. Surface marked by concentric striae. Hinge line thin, 

 arched, lacking teeth. Ligament external, resting in a groove 

 along the hinge line. Pallial line simple. Devonic-Carbonic. 



41. E. philippi Hall. (Fig. 493, a.) Devonic. 



Distinguished by its broadly oval form, at times almost circular, 



Fig. 493. a, Edmondia philippi ; b, E. subovata, right valve ; c, E. burlingtonensh. 



(Pal. N. Y., V.) 



by the nearly central beaks, and by the fine concentric striae which 

 often become lamellose. 



Chemung Group : New York, Pennsylvania. 



42. E. subovata Hall. (Fig. 493, b.) Devonic. 

 Elliptical. Beaks somewhat anterior. 



Chemung : New York, Pennsylvania. 



43. E. burlingtonensis White and Whitfield. (Fig. 493, c.) 



Mississippic. 

 Differs from E. subovata in the more anterior beaks and in the 

 straighter base. 



Lower Mississippic of Ohio, Iowa, Missouri. 



Fig. 494. Edmondia aspinwaflensis, right and cardinal views. (Ind. Surv. ) 



44. E. aspinwallensis Meek. (Fig 494, a-b.) Miss.-Carbonic. 



Greatest convexity of valves is in front of middle. 



Mississippic of Utah ; Coal Measures of West Virginia to Ne- 

 braska and Missouri. 



