PLATE XX. 



Fig. 1 a. — DIthj/rocdris riranulata, W. & E. Carapace flattened, open. X 2^. 

 B. M., 59541. No. 9 ; also P). XVTII, fig. (i. (Page 144.) 



Fig. 1 I) — The same. Two cephalic and one michal ridge. X 5. 



Fig. 2 a.—D. (/ranvlafa, W. & E. Left valve. X 2^. M. G. S. Sc, F %^, 

 No. 6 ; also PI. XVIII, fig. 4. (Page 142.) 



Fig. 2 b. — The same. Part of surface, including the dorsal ridge. X 14. 



Fig. 2 c. — The same. Outline of the ridge. X 14. 



Fig. 2 (/. — The same. Part of the surface. X 40. 



Fig. 3 rt.. — D. i/ran>il(ita,W. & B. Carapace, somewhat crushed. X 2-|. B. M., 

 59541, No. 10 ; also PI. XIX, fig. 6. (Page 144.) 



Fig. 3 /;. — The same. Outline of the elevation of the carapace. X 2^. 



Fig. 3 c. — The same. One of the cephalic ridges. X 5. 



Fig. 3 d. — The same. View of the broken end of the dorsal ridge. X 10. 



Fig. 3 e. — The same. Part of the surface. X 40. 



Fig. 3/. — The same. Outline of the elevation of the dorsal ridge. X 15. 



Fig. 3r/. — The same. Part of the dorsal ridge. X 15. 



