Hello Emmanuel,

B. tricincta and C. ventricosa are somewhat similar in appearance.  They
are both usually uniform gray in color (though C. ventricosa is usually
lighter in color), but B. tricincta is more ovoid in shape, with less
lateral expansion of the lip, which often extends posterior to the
depressed spire.  C. ventricosa has an erect spire, and the lip does not
extend posterior to the shoulder.  I agree with Bob that the shell
labeled B. tricincta on the website is C. ventricosa.  If you have
access to the Compendium of Seashells, both these species are pictured
there, on the same page.

Paul M.