Looks to me like a beach worn Conus catus.
Interesting. I can see that for the upper portion, but why would the bottom portion be yellow like that? I've never seen such a distinct separation of colour. If it was a worn specimen, why wouldn't the bottom be plain white instead? I've seen brown ones and yellow ones, but not both at once. Strange indeed.
Thanks
It does happen sometimes that shells are sort of 'divided' colour wise, but maybe this one's base was sticking out of the sand and was more faded by the sun that the rest of it.
If you look these over you 'll see just how variable this species can be.
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Hey, now that I see that, it does look like a worn out version of the fourth one in the fifth row. Neat. Thanks a bunch!