I looked them up in Fenner and Calfo's Reef Invertebrate book. A few paragraphs that say little more than they probably don't ship well and they should probably be in a species tank <read: We have no idea, but here are some pictures.>
I googled around a little bit, and found this FAQ. They may lose their anemones, either because of conditions, or because of the molt, and their claws are pretty useless without them. They may be able to eat prepared food even without them, though.
I couldn't link it directly, so scroll down and click on boxing crab care.
http://saltaquarium.about.com/cs/crabcare/
From what I can tell, the anemone they carry is a species of Telmatactis. Maybe that will help.