PLATE 33. 

 Fig. 1. 173. 6. Atrypa extans. (Pag. 137.) 



1 a. Dorsal valve. I b. Ventral valve. 



Fio-. 2. 174. 7. Atrypa nucleus. (Pag. 138.) 



2 a. Ventral valve. i b. Dorsal valve. 2 c. Profile view. 



Fig. 3. 176. 9. Atrypa bisulcata. (Pag. 139.) 



3 a. Dorsal valve. 3 b. Ventral valve. 3 c. Cardinal view. 3 d. Enlarged profile view. 3 e. Front view. 



Fig. 4. 177. 10. Atrypa deflecta. (Pag. 140.) 



4 a. View of dorsal valve. 4 b. Front view, showing tlie form of the two valves. 



Fig. 5. 178. 11. Atrypa recurvirostra. (Pag. 140.) 



5 a. Dorsal valve. 5 4. Profile view. 6 c. Cardinal view. 5 d. Ventral valve separated from the dorsal. 



Fig. 6. _ 179. 12. Atrypa exigua. (Pag. 141.) 



6 a. Ventral valve. 6 b. Dorsal valve. 6 c. Cardinal view. 6 d. Dorsal valve of a small and large individual. 



Fig. 7. 181. 14.' Atrypa circulus. ' (Pag. 142.) 



7 a. Dorsal valve. 7 b. Cardinal view. 7 c. Profile view. 



Fig. 8, 9. 182. 15. Atrypa AMBiGUA. (Pag. 143.) 



8 a & 6. Usual form of the shell. 8 c. Front view in outline, showing two incipient plications in the sinus. 

 \). Four valves represented precisely as they occur on the surface, of a slab of limestone. 



Fig. 10. 183. 16. Atrypa hemiplicata. (Pag. 144.) 



10 a. Dorsal valve of a specimen of the ordinary size. 10 b. Profile view. 10 c. Front view. 



10 d. Dorsal valve and front view of a young specimen. 



10 c. Ventral valve of a large specimen. 10/. Front view of the same. 



Fig. 11. 184. 17. Atrypa (perhaps the young of j4. ea;<a»w). (Pag. 145.) 



11 a, 6. Ventral and dorsal valves. 11 c. Front view, the dorsal valve below. 11 d. Profile view. 



Fig. 12. 185. 18. Atrypa subtkigonalis. ( Pag. 145.) 



1'2 a. Ventral valve. 12 b. Profile view. 12 c. Front, with the dorsal valve below. 



Fig. 13. 186. 19. Atrypa increbescens. (Pag. 146.) 



13 a, b. Ventral valve and front view. 13 /, m, n, v. Ventral valves and front views of two 



13 c, d. Ventral valve and profile view. larger individuals. 



13 e,/. Ventral valve and profile view of a more 13 p,r,s. Ventral valve, profile and front view of a 



gibbous form. larger specimen. 



IS g, h,i. Front, profile, and ventral valve of a larger 13 t, u. Profile and front view of a gibbous specimen. 



and more rotund specimen. 13 w. Profile view of a very gibbous specimen. 



13 At. a small specimen of the western type. 13 x, y. Front and cardinal view of the same. 



Fig. 14. 187. 20. Atrypa dentata. (Pag. 148.) 



14 a. Dorsal valve. 14 6. Front view of the same, the dorsal valve below. 14 c. Profile view. 



Fig. 15. 180. 13. Atrypa modesta. (Pag. 141.) 



The two upper figures are of the dorsal and ventral valve ol' a specimen above the common size ; the lower 

 figure is of a small specimen, having the same characters. 



Fig. 16. 188. 21. Atrypa sordida. (Pag. 148.) 



