Imbricaria hidalgoi (Sowerby, 1913)
Initially as Imbricaria salisburyi (Drivas & Jay, 1990) but it is restricted to the Indian Ocean; I. hidalgoi is the Pacific Ocean counterpart. The two are closely related.
These will turn up in deeper water, typically starting around 70 ft. This one was from Agat Bay, Guam. (aquarium photo, slide duplication, original on Fujichrome Provia).