PLATE 56. 



Fig. 1. 631. 4.5. Atrypa rugosa. ( Pag. 271.) 



1 a. The dorsal valve of a young individual, vv^hich is marked by two stronger plications in the centre. 



1 6. Cardinal view of the same, showing the neail}' flat ventral valve. 



1 c. Ventral 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 /. 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 i. Profile view of the same. 1 ?«. Dorsal valve of a large individual. 



1 n. An enlargement of the plicatioiis, showing character of surface. 



Fig. 2. 632. 46. Atrypa nodostriata. (Pag. 272.) 



2 a, 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, I. Dorsal, ventral and profile views of a more rotund form. 



2 m, n. Ventral 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. 



Fig. 3. 633. 47. Atrypa camura. ( Pag. 273.) 



3 a, h. Ventral and profile views of a young specimen. 



S c, d. Ventral and dorsal views of a larger specimen than the preceding. 



3 e. Ventral 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 I, m. Views of a more rotund specimen, showing the beak much reduced, with the foramen not surrounded. 



3 n, 0. Specimens which are more extended laterally than the preceding forms. 



3p, 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. 



