Hmm, that's kind of small for a Scutus that large, if its shell is the size of the reddish patch. There aren't a whole lot of choices. It's definitely not a chiton. There are only a handful of molluscan options, and most can be eliminated because of characteristics that are missing. See the line straight down the dorsum on the first pic? That's typical of molluscs that have a mantle which meets in the middle, and shows part of the shell when the mantle edges are retracted a bit to either side. Cowries do this, but they can and will withdraw the mantle completely when you touch them. Most of the time when you can see a white longitudinal line on the dorsum, it's a Scutus. I've just never seen one so ornate. If it were mine, I'd touch it with two fingers, one on each side of the shell, and see if I could separate the mantle. You should be able to do this gently without harming the animal. If there is no mantle break, then the animal in the lower pic is a diffrerent species than the one in the top pic. I'd bet it's going to be Scutus unguis or Scutus sinensis, though, and that you'll be able to see part of the shell.
Interesting animal. Cheers again,
Don
