[SPOILER ALERT]
http://img59.imageshack.us/img59/1534/dharma6ul.jpg
that was the symbol in the bunker that Ana Lucia's group found. I think the arrow bunker is the top bunker on the map. It looks like there could be an arrow up there in that bunker, and it also looks like it says, "Arrow"
The other thing on the map is the "CV" rectangles. There are a bunch of them, 3 are near the hatch. And the writing says, "Possible CVII inactive since accident"