Crab ID please
 

ok so i found a crab tonight....and sorry not fast enough to get a pic, will try again tomorrow night but hoping someone might be able to ID....
it was smaller, body approx 1/4" , seemed to be more of a charcoal grey than a black, eyes were black and front pointy claws were red, and had a white triangle on its head. any thoughts? or sights I can search to ID myself?