Bad cowries

[Emma]

Hello Pierre!

I'd say the first and the third are Mauritia arabica (I have some in similar condition from Papua New Guinea). If you cover the top of a Mauritia arabica in acid it is purple (I was given one, I haven't done this myself); you also see this purple covering in other cowries (annulus, if I am not mistaken).
With regard to the Bulla stage, I'm not so sure, I'd suggest Chelycypraea testudinaria; I don't think it is tigris this time. But, as always, I am not sure of the location of C. testudinaria so somebody will probably correct me.

I hope this helps,

Best wishes,

Emma.