PLATE V 



ONTOGENY OF SIX SPECIES OF CERITHIUM (continued) 



Fig. 1. Ccrithiiim adansoni, ninth volution. 12 X 7 mm. 



Fig. 2. Cerithium adansoni, aperture. 16 X 12 mm. 



Fig. 3. Cerithium wquispirale, ninth volution. 2.5 X 1.4 mm. 



Fig. 4. Cerithium ccquispiralc, twelfth volution. 4.4x8.5 mm. 



Fig. 5. Pseudovertagus aluco, tenth volution. 10 X 4.5 mm. 



Fig. 6. Pseudovertagus aluco, eleventh volution. 16 X 7 mm. 



Fig. 7. Cerithium lanieUosum, ninth volution. 3.4 X 1.5 mm. 



Fig. 8. Cerithium lamcUosum, eleventh volution. 6 X 3.5 mm. 



Fig. 9. Cerithium retardatuni, ninth volution. 3.8 X 1.8 mm. 



