PLATE IV 

 ONTOGENY OF SIX SPECIES OF CERITHIUM (continued) 



Fig. 1. Cen";f7w«m /M6eros?(m, eighth volution. 4.6 X 2.2 mm. 



Fig. 2. Cerithium adansoni, fifth volution. 3.5 X 1.5 mm. 



Fig. 3. Cerithium adansoni, eighth volution. 9 X 3.4 mm. 



Fig. 4. Cerithium? nodulosum, sixth volution. 6X3 mm. 



Fig. 5. Cerithium? nodulosum, eighth volution. 6 X 5 mm. Later whorls of 



this shell are not figured, as they are too large to show details when 



reduced to the scale of this plate. 

 Fig. 6. Pseudovertagus altico, seventh volution. 5.2 X 2.3 mm. 

 Fig. 7. Pseudovertagus alnco, eighth volution. 7x3 mm. 

 Fig. 8. Cerithium lamellosum, fifth volution. 1.2 x .5 mm. 

 Fig. 9. Cerithium retardatiim, fifth volution. 1.2 X .5 mm. 

 Fig. 10. Cerithium retardation, seventh volution. 2x1 mm. 



