Forums SEASHELL-COLLECTOR

I collected this shell from dredged material from the Red Sea, Saudi Arabia many years ago.
It would appear to be a specimen of Casmaria ponderosa, (Syn. Cassis ponderosa) but it has a diagonal rib with the same markings as that around the aperture.
Could this be a freak or have I miss-identified it?
It is 45 mm in height.

This is Casmaria ponderosa. A misplaced varix like this can occur in any species of Cassidae. It indicates the location of the shell lip during a past period of restricted shell growth, which could be caused by a period of unusually low temperature, or a period when food was scarce, etc.

Thank you for this explanation.