PLATE 59. 



Fig. 1. 472. 6. AvicuLA emacerata. ( Pag. 282.) 



1 a. A young individual of this species, having the radiating and concentric stria3 equally developed. 



1 6. A larger individual : this one is about the ordinary size of the specimens obtained. 



1 c. A large individual, preserving the surface markings in a good degree of perfection. 



1 d. The right valve of this species, showing the plain nearly flat body of the shell, and striated wing. 



1 e. An enlargement of a portion of the surface, showing the character of the diverging and concentric strise. 



Fig. 2. 644. 8. AvicuLA UNDATA. (Pag. 283.) 



Fig. 3. 645. 9. Avicula subplana. (Pag. 283.) 



3 a. A left valve of ordinary size, where the extremity of the cardinal line is extended slightly beyond the 



width of the shell. 

 3 6. A larger shell, where the cardinal line is less extended than the width of the shell. 

 3 c. A fragment of shale with the right valves of two individuals, showing a greater extension of the cardinal 



line, and a more distinct wing than in the left valve. 



Fig. 4. 646. 10. Avicula? orbiculata. (Pag. 284.) 



Fig. 5. 647. 2. Posidonomya? rhomboidea. (Pag. 284.) 



Fig. 6. 648. 22. Modiolopsis? undulostriata. . (Pag. 284.) 



6 a. The shell, natural size. 6 6. A portion of the surface enlarged. 



Fig. 7. 474. 19. Modiolopsis siTBALATUsI (Pag. 285.) 



Fig. 8. 478. 4. Orthonota cuETA? , (Pag. 285.) 



