This spider was killed when my wife lifted up a half-buried rock in our front yard in hot springs, arkansas. The moment the crowd of twenty or so were exposed, they rushed her like an army. She killed the one that managed to make it to her shoe. She was not bitten. Very aggressive little buggers. No idea what they are or where they disbursed to. We nuked the nesting area. Any clue as to what this WAS? :-)
It is difficult to be certain without seeing a dorsal view, but this might be a woodlouse spider (Dysdera crocata; family Dysderidae) - see http://tinyurl.com/y7too7j for an example. They have very large chelicerae ('jaws') in proportion to their body size, and can inflict a painful (but not dangerous) bite if mishandled. They don't appear to be truly aggressive, but will definitely defend themselves if threatened.
