PLATE 24. 



Fig. 1. 464. 35. Atrypa naviformis. (Pag. 76.) 



1 a. View showing the ventral valve, with the elevated beak of the dorsal valve. 

 1 b. View of the dorsal valve of a full grown shell, 

 1 c, d. Front and cardinal view of the same shell. 

 1 e. Profile view of the same. 1 /. A portion of the surface enlarged. 



1 g, h, i, k. Several views of a young shell, the front 1 i showing a scarcely formed sinus, contrasting in 



this respect very strongly with fig. 1 c. 



Fig. 2. 465. 36. Atiitpa cylindrica. (Pag. 76.) 



2 a.- View of the ventral valve, showing the beak of the dorsal valve elevated above it. 

 2 b. Dorsal valve of the same. 2 c. Profile view of the same. 



2 d, e, f. Ventral, dorsiil and profile views of a .smaller shell. 



2 %. Cardinal view of the last. 2 h. Front view of the same. 



Fig. 3, 4. 466. 37. Atrypa intermedia. (Pag- 77.) 



3 a. View of the ventral valve. 3 6. Profile of the same. 3 c. Cardinal view. 

 3 d. Front view, showing the scarcely sinuous margins. 



3 e. A specimen with tlie shell partially removed, showing three strong elevated lines in the cast. 



3 _/". A cast of this species. 



4 a, 4, c, d. Ventral, profile, cardinal, and front views of a young shell, apparently of the same species. 



Fig. 5. 467. 38. Atrypa (cast). ( Pag. 78.) 



5 a. Cast of dorsal valve. 5 6. Profile of the same. 



Fig. 6. 468. 39. Atrypa cylindrica? (cast). ( Pag. 78.) 



6 a. Dorsal view of cast. 6 6. Profile of the same. 



Fig. 7. 471. 2. Pentamerus fornicatus. ( Pag. 81.) 



7 a. Ventral valve, with the large elevated beak of the dorsal valve incurved over it. 

 7 6. Dorsal view of the same specimen. 



7 c. Cardinal view, showing the great convexity of the dorsal valve. 

 7 d. Profile view of the same. 



