PLATE V 



ONTOGENY OF SIX SPECIES OF CEKITHIUM (continued) 



Fig. 1. Veritliiiuii adansoni\ ninth volution. 12 X 7 mm. 

 Fig. 2. Cerithlmn adansoni, aperture. 16 X 12 mm. 

 Fig. .3. Cerifhiiini cequispirale, ninth volution. 2.5 X 1.4 mm. 

 Fig. 4. Verithinin cequispirale, twelfth volution. 4.4 X 8.5 mm. 

 Fig. 5. Pseudovertagus aluco, tenth volution. 10 x 4.5 mm. 

 Fig. 6. Pseudovertagus aluco, eleventh volution. 16 X 7 mm. 

 Fig. 7. Cerithium lamellosum, ninth volution. 3.4 X 1.5 mm. 

 Fig. 8. Cerithium lamellosuDi, eleventh volution. 6 X 3.5 mm. 

 Fig. 9. Cerithium retardatum, ninth volution. 3.8X1.8 mm. 



