PLATE VII 



ONTOGENY OF CERITHIID^ 



Fig. 1. Cerithium caUisoiua, third volution. .8 X .3 mm. 



Fig. 2. Cerithium menkei, second volution. .2 x .6mm. 



Fig. 3. Cerithium menkei, fourth volution. 1.8 X .8 mm. 



Fig. 4. Vicinocerithimn parallelum, second volution. 1.2 X .5 mm. 



Fig. 5. Yicinocerithiiim parallelum, third volution. .2 X .8 mm. 



Fig. 6. Ticinoeerithium bouei, fourth volution. 1.4 X .6 mm. 



Fig. 7. Potamidopsis tricarinata, second volution. .4 X .19 mm. 



Fig. S. Potamidopsis tricarinata, third volution. .6 X .3 mm. 



Fig. 9. Potamidopsis troclileare, fractured protoconch. .4 X .3 mm. 



Fig. 10. Potamidopsis troclileare, fourth volution. 1 X .4 mm. 



