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Rabidosa rabida
I've seen a smaller wolf spider with babies and it was a little creepy but kool to see.
Here is an additional link from Texas A&M. Do not let the name scare you. They are shy and very good spiders to have. After she the babies in her egg sack hatch, they will ride around on her back for a time. That is when she looks most scary. If disturbed they will run away, but then when safe, come back and climb on again.
Nice spotting with the egg sac. BugGuide.net maybe can help ID or looking through this list: http://en.wikipedia.org/wiki/List_of_spi...