PELECYPODA—PRIONODESMACEA. 



391 



52. P. robusta Hall. (Fig. 498, a.) Devonic. 



Much like P. dichotoma but the plications are more elevated and 

 angular and rarely bifurcate. 



Portage Group : New York. 



FlG. 498. a, Panenka robusta, left valve ; b, P. costata, left valve. (N. Y. Surv.) 



XXII. Ontaria Clarke. {Cardiola Broderip in part.) 

 Equivalve, exceedingly thin ; beaks not very prominent, turned 

 posteriorly. Cardinal area beneath the beak nearly extinct. Sur- 

 face covered with fine concentric and radiating striae. Devonic. 



Fig. 499. Ontaria sub orbicularis, X 2 > vvith enlargements jaf cardinal region, X 5- 



(N. Y. Mem., 6.) 



53. 0. suborbicularis (Hall). (Fig. 499.) Devonic. 



Suborbicular ; beak central to subcentral. Surface marked 

 with sharp, imbricating concentric striae ; very fine radial striae may 

 be present. 



Portage (Naples fauna) of New York. 



