Uh oh, looks like you took your pics down. Anyway Chuck, it looks like it's a juvenile Tectus pyramis. The thing that bothers me is that the nodules are lined up into rows, and they usually aren't on that species. Tectus fenestratus DOES usually line up like that, but it has a row of nodules at the base that makes it look like it isn't sharp edged, while yours looks very sharp and angular. I've found similar shells in Samoa, and questioned whether they were variations of one of those species, hybrids between the two, or something else entirely. I checked Poppe's new Philippine shell book, and it doesn't look much like anything in there other than the ones I mentioned, and the same goes for Springsteen & Leobrera. If it's really that common, it should be there for sure. The only other thing that throws me off is the "crinkles" that are slanted across the whorls on the lower part of the shell. That's typical of several species of Astraea, but I've never seen it on an Indo-Pacific trochid...that's why I asked you about the operc, but I think I can see the hermit crab's legs in your shell, so you may have to catch a live one to verify which type of operculum it has. When you catch another live one, can you post pics for me?
Thanks,
Don
