404 NEW YORK STATE MUSEUM 



PLATE 8 



Genus ontaria gen. nov. 



Page 279 



Ontaria suborbicularis Hall (sp.) 



Page 282 



i A left valve with smooth surface 



2 A right valve with concentrically lined surface 



3 A left valve radially lineate outside the single strong growth 



line 



4 A right valve with radial striations and distant growth lines 



5 Profile of a valve showing an abrupt marginal deflection 



6 Enlargement of surface of frontal slope on the preceding, 



showing cancelating striae. X3 



7 A right valve with regular and sharp concentric lines 



Naples subprovince Naples 



8 Interior of the umbonal region from a barite replacement. X5 



9 Cardinal view showing the very narrow cardinal area. X5 



10 Cardinal view of another replacement. X5 



Naples subprovince Honeoye lake 



11 A right valve with radially striated surface, xi.5 



Naples subprovince Naples 



L2 A left valve with sharp concentric lines 



Cashaqua shale Attica 



13 A left valve with sharp concentric lines about the margin 



14 A left valve with concentric lines only 



15 A left valve with both concentric and radial striae 



16 A right valve with cancelating striae 



1 7 A valve with subcentral beak and sharp regular concentric 



striae. X2 



18 A right valve with obscure concentric markings and well 



marked larval shell. X2 



19 A right valve, oblique in form and concentrically marked. xi„5 



