Help ID this crab?

[rgonzalez]

I found this guy sitting on the bottom of my sand bed. I'd seen him in my rockwork before, but never saw his full body. I'm not sure if this is his molt or if his carcass. Either way, anyone know what type of crab it is?

 

[Lolas_boy]

Not sure what kind it is, but I assume it is bad. I heard somewhere that black claws are a sign, along with rounded or pointy claws.

 

[gtstylez87]

its a type of stone crab

 

[silberspieler]

I have the same in my tank, is not aggressive