Welcome to Reef2Reef!
I really need to work on familiarizing myself with crab taxonomy more (I'll get around to it eventually), as this is like the fifth brown and white crab that's popped up in the past few months that I haven't been able to ID properly.
I can tell you for sure that it's not a Calico Crab or
Lissocarcinus laevis (sorry MoshJosh - the colors are right though).
At this point, my best guess is a Xanthid (Stone/"Gorilla") crab of some kind, probably an Atergatis species, as I know of a few species in that genus with a similar pattern and color on the shell (see the links below).
Atergatis sp.01 is commonly referred to as Atergatis sp.. Difficulty in the aquarium: Easy. A aquarium size of at least 50 Liter is recommended. Toxicity: Toxic.
www.reeflex.net
Atergatis floridus is commonly referred to as toxic tiny crab, floral egg crab, green egg crab or shawl crab. Difficulty in the aquarium: Very easy. Toxicity: toxic.
www.reeflex.net
Atergatis sp.02 is commonly referred to as crab. Difficulty in the aquarium: There are no reports available yet that this animal has already been kept in captivity successfully. Toxicity: Toxic.
www.reeflex.net
With regards to the "Gorilla" name for crabs (the discussion was on emerald crabs with furry legs):