PLATE IX 



ONTOGENY OF CERiTHiiD.E (continued) 



Fig. 1. Cerithium calUsoma. tenth volution. 7.3 X 7 mm. 



Fig. 2. Cerithium menkei. tenth volution. 1.3 X 11.5 mm. 



Fig. 3. Vicinocerithium parallelnm, twelfth volution. 6 X 4 ram. 



Fig. 4. Vicinocerithium paraUeJum. apertui-e. 9.8X8 mm. 



Fig. 5. Vicinocerithium bouei. twelfth volution. 3x2 mm. 



Fig. 6. Vicinocerithium bouei. aperture. 8.5 X 6.5 nmi. 



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



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



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



