514 



NORTH AMERICAN INDEX FOSSILS. 



lateral teeth present. Ligament external, attached to thickened 

 margin of shell which is often longitudinally grooved for its recep- 

 tion. Pallial line simple. Devonic. 



413. M. complanata Hall. (Fig. 691, a.) Devonic. 

 Large. Margins regularly rounded. 



Onondaga : New York, Ohio. 



414. M. mytiloides Hall. (Fig. 691, £.) Devonic. 

 Above medium size, oblique. Basal margin nearly straight or 



Fig. 692. a, Modiomorpha quadrula ; b, M. subalata ; 



(Pal. N. Y., V.) 



M. alia; d, M. concentrica. 



very slightly concave anterior to middle. Cardinal margin arcuate. 

 Anterior end narrowed and extended. 



Hamilton : New York, Pennsylvania, Indiana ? 

 415. M. alta Hall. (Fig. 692, c.) Devonic. 



