PLATE IX 



ONTOGENY OF cERiTHiiD^ (continued) 



Fig. 1. Cerithium callisoma, tenth volution. 7.3 X 7 mm. 



Fig. 2. Cerithium menkei, tenth volution. 13 X 11.5 mm. 



Fig. 3. Vicinocerithium parallelum, twelfth volution. 6 X 4 mm. 



Fig. 4. Vicinocerithium parallelum. aperture. 9.8 X 8 mm. 



Fig. 5. Vicinocerithium houeU twelfth volution. 3 X 2 mm. 



Fig. 6. Vicinocerithium touei, aperture. 8.5 X 6.5 mm. 



Fig. 7. Potamidopsis tricarinafa. twenty-third volution. 12 X 5 mm. 



Fig. 8. Potamidopsis tricarinata. twenty-fourth volution. 19 X 11mm. 



Fig. 9. Potamidopsis trochlears aperture. 11.8 X 7.5 mm. 



