Indian Ocean Cerithium

[conchylinet]

Hello,
Below are some Cerithidae from mauritius, they dont look quite the same (size from L2R: 28mm, 38mm, 31mm). Any help on the specie(s) would be welcome (I am puzzled between C.dialeucum and C.columna)

<img src="http://www.conchylinet.com/Images/Misc/cerithidae090901.jpg" alt="http://www.conchylinet.com/Images/Misc/cerithidae090901.jpg" style="border:0" />

Thanks
Pierre