108 
Gustaf T. Troedsson 
Plate I. 
1. Ventral valve. 
2. Dorsal valve. 
3. Ventral valve. Side views (a, b) and outline of back view (c). 
4. Interior of dorsal valve. 
5. V entrai valve. 
6. Ventral valve. 
7. Dorsal valve. 
8. Internal cast of ventral valve. 
9. Internal cast of dorsal valve. 
10. Ventral valve. 
11. External cast of dorsal valve. 
12. a. Internal cast of ventral valve, b. Back view. c. Outline of convexity. 
13. 
14. a. Part of whorl showing the striation, b. Outline of convexity of whorl. 
15. 
16. 
17. On the last whorl a part of the glossy shell is preserved. 
18. a. Ornamentation of shell near the aperture, b. Outline of shell. 
19. a. Cephalon. b. Pygidium. 
20. Part of thorax. 
21. Hypostome. 
22. Hypostome from young specimen. 
23. Pygidium, nepionic stage. 
24. 
25. 
26. Cephalon. 
27. 
28. 
29 . 
