Identificaciones de kemper

I'm fairly sure these are the same old wives that I have already posted from this dive,with that submission having showed the species tendency to form almost symmetrical V shaped lines facing the current, presumably as a defence strategy at times of significant predation risk.

Shore diving at Pupukea Beach Park, max depth 39 ft/12m.

Not entirely sure of ID, but Hoover notes that in this species the sides of the shell are fused and it can't close. Certainly me bumbling around near it with a camera didn't make it close.