PLATE 56. 
1. 631. 45. Atrypa rtjgosa. (Pag. 271.) 
1 a. The dorsal valve of a young individual, which is marked by two stronger plications in the centre. 
1 b. Cardinal view of the same, showing the neaily flat ventral valve. 
1 c. Yentral view of a larger specimen, where the mesial lobe and sinus are developed. 
1 d. Profile view of the same specimen, showing convexity of both valves. 
1 e. Front view of the same. 
1 f. Dorsal valve of another specimen, where the sinus is less developed. 
1 g. Front view, showing the slight mesial depression and elevation. 
1 h, i. Dorsal and ventral valves of a specimen of medium size. 
1 k. Front view of the same, showing the strong elevation in the centre. 
1 l. Profile view of the same. 1 m. Dorsal valve of a large individual. 
1 n. An enlargement of the plications, showing character of surface. 
2. 632. 46. Atrypa nodostriata. (Pag. 272.) 
‘La, b. Dorsal and ventral views of a young specimen. 
2 c. Profile view of the same specimen, which is compressed. 
2 d, e. Dorsal and ventral views of a specimen below the medium size. 
2 /. Profile, view of the same. 
2 g, h. Dorsal and ventral views of a specimen of medium size, which is slightly more elongated than usual. 
2 i, k, l. Dorsal, ventral and profile views of a more rotund form. 
2 m, n. Yentral and profile views of a large specimen in its natural condition. 
2 o. Profile view of a larger specimen which is extremely compressed. 
2 p. The plications enlarged, showing the imbricating lamellae. 
2 r, s, t, u. Front views of different specimens, showing the absence of a sinus in the young shell, and its 
increase as the shell becomes larger. 
3. 633. 47. Atrypa camfra. ( Pag. 273.) 
3 a, b. Yentral and profile views of a young specimen. 
3 c, d. Yentral and dorsal views of a larger specimen than the preceding. 
3 e. Yentral view of a specimen having the beak of the dorsal valve well preserved!. 
3 /. The beak of the same enlarged, showing the foramen. 3 g. Profile view of the same. 
3 h. Dorsal view of a specimen, larger than the preceding. 
3 i, k. Dorsal and ventral valves of a larger compressed specimen. 
3 l, m. Views of a more rotund specimen, showing the beak much reduced, with the foramen not surrounded. 
3 n, o. Specimens which are more extended laterally than the preceding forms. 
3 p, r. Front views of two specimens, showing slight indications of a sinus. 
3 t. The beak and foramen of a full-grown individual. 
3 u. Enlargement of the surface of this species. 
