What is this cool looking creature

[javman9]

Hi I've seen these while on vacation and they get quite large should I be worried?

 

[cloak]

Chiton. (good)

 

[erinmegan85]

+1 on chiton.

 

[MicroPico]

It is a chiton. Good guy. Pretty cool and interesting too. My lfs had several real large ones for sale and they look like those pill bugs that are in people's gardens, under rocks. Kind of prehistoric looking.

 

[javman9]

Thanks definitely cool!