NIAGARA GROTTP. 



285 



The only specimen seen is imperfect at the anterior extremity, the posterior extremity and 

 beak alone remaining. 



Fig. 6 a. The shell, natural size. 



Fig. 6 S. A portion of the surface enlarged. 



Position and locality. In the shale of this group at Lockport. 



474. 19. MODIOLOPSIS SUBALATUS? 



PL. LIX. Fig. 7. 

 Compare M. aubalatus, page 84 of this volume, pi. 17, figs. 5 and 6. 

 Obovate, the posterior extremity rounded, and broader than the anterior extremity ; umbo 

 slightly prominent, and elevated above the cardinal line ; surface marked by fine concentric 

 striae. 



This is apparently a large individual of M. subalatus of the Clinton group. It differs from 

 the other species of this genus in the narrow anterior extremity being proportionally more 

 extended, with little evidence of the strong muscular impression. 



Position and locality. In the shale of this group at Wolcott. 

 478. 4. ORTHONOTA CURTA? 



PL. LIX. Fig. 8. 

 Reference O. curta, p. 86 of this volume, pi. 17, fig. 11. 

 A fragment of slate, presenting a cardinal view of the two valves of a species of Orthonota. 

 From the condition of the specimen, it is impossible to determine any difference between it 

 and the species of the Clinton group. 



Position and locality. In the shale of the group at Wolcott. 



