PLATE VIII 



ONTOGENY OF CEEiTHiiDiE ( Continued) 



Fig. 1. Cerithimu callisoma, sixth volution. 1.8 X. 8 mm. 



Fig. 2. Cerithium callisoma, eigbtli volution. 2.G X 1mm. 



Fig. 3. CeritJiium menkei, fifth volution. 1.8 X 1 mm. 



Fig. 4. Vicinocerithium paraUelmn, fifth volution. 2.4 X 1 mm. 



Fig. 5. Vicinocerithium parallelum, seventh volution. 3 X2mm. 



Fig. 6. Vicinocerithium houei, eighth volution. 2.8 X 1.4 mm. 



Fig. 7. Potamidopsis tricarinata, sixth volution. 1.4 X .6 mm. 



Fig. 8. Potaiitidopsis tricarinata, tenth volution. 2.7 X 1mm. 



Fig. 9. Potaiitidopsis trochlcare, sixth volution. 1.3 X .5 mm. 



Fig. 10. Potamidopsis trochleare, twelfth volution. 11.8 X 7.5 mm. 



