PLATE 58. 
Fig. 1. 639. 53. Atrypa brevirostris(?). ( Pag. 278.) 
1 a, b. Ventral and dorsal views of a specimen. 1 c. Profile view of the same. 
1 d. Cardinal view. 1 e. Front view. 
1 f. An enlargement of the plications, showing concentric striae. 
Fig. 2. 640. 54. Atrypa obtusiplicata. (Pag. 279.) 
2 a, b, c. Ventral, dorsal and profile views of a specimen of the ordinary size. 
2 d. Front view of the same. * 
2 e. Ventral view of a specimen which is more expanded at the sides. 
2 f. Front view of a specimen where the ventral valve is much elevated, and the sinus very deep. 
2 g. Ventral valve of a compressed specimen. 
2 h. Several plications enlarged, showing the concentric striae. 
Fig. 3, 4. 641. 55. Atrypa plicatella ? ( Pag. 279.) 
3 a, b. Ventral and dorsal views of this species. 
3 c. Cardinal view of the same. 3 d. Profile view. 
3 e. Several of the plications enlarged, showing the concentric striae. 
4 a, b. Dorsal and profile views of a larger specimen, showing a greater number of plications than the spe¬ 
cimen fig. 3. This is probably only a variety of the same species. 
Fig. 5. 643. 57. Atrypa corallifera. ( Pag. 281.) 
5 a. A young individual of this species. 5 b. A larger specimen of this species. 
5 c, d. Ventral and dorsal views of a specimen of the ordinary or prevailing size. 
5 e, f, g, h. Front views of different specimens, one of which is compressed, and the others retain their 
natural proportions. 
5 i. k. Profile views of two individuals, one of which is very gibbous. 
5 l. 7>i. Cardinal views of other individuals. 
5 », o. Casts of the dorsal valves of two individuals, the last one larger and proportionally more extended 
laterally than any other specimen observed. 
5 p. Cast of the ventral valve. 
5 r. An enlargement of the surface, presenting its ordinary character. 
5 s. An enlargement of the surface, where the shell is thickened, and the spaces between the reticulate 
openings is punctate. 
5 t. An enlargement of the surface of the cast of this species, showing the punctate character. 
