PLATE 58. 



Fig. 1. 639. 53. Atkypa brevirostris(?). (Pag- 27S.) 



1 a, b. Ventral and ilui'sal views of a specimen. 1 c. Profile view of the same. 



1 d. Cardinal view. 1 c. Front view. 



1 f. An enlargement of the iilieation.s, .showing concentric stria?. 



Fig. 2. 640. 54. Atrypa obtusiplicata. (Pag. 279.) 



2 a, b, c. Ventral, dorsal and [irulilc views of a specimen of tlie ordinary size. 

 2 (/. Front view of the same. 



2 e. Ventral view of a specinun which is more c.vpandcd at the sides. 



2 /. 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. Athypa plicatella ? ( Pag. 279.) 



3 a, h. 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 stride. 



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 corallifeea. (Pag. 281.) 



5 a. A young individual of this species. 5 6. A larger specimen of this species. 

 5 c, d. Ventral and dors,al views of a specimen of the ordinary or prevailing size. 



5 c,/, g, h. Front views of difTerent 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 I, 7)1. Cardinal views of other individuals. 

 5 n, 0. Casts of the dorsal valves of two individuals, the last one larger and proportionally more extended 



laterally tlian any other specimen observed. 

 5 p. Cast of the ventral valve. 



5 r. An enlargement of tlie surface, presenting its ordinary character. 

 •I 5. 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. 



