PLATE III. 



PAGE 



Fig. 26. Pachypoma btanqulata. Natural size. 15 



Fig. 27. Ptychosttlis caffea. Slightly magnified. 16 



Fig. 28. Calliostoma tricolor. 17 



Slightly magnified from a recent specimen. 



Fig. 29. Indet. Natural size. 17 



Fig. 30. Indet. Natural size. 17 



Fig. 31. Zirphjsa dentata. Natural size. 18 



31 a. Top view of the dorsal plate. 



