My spider was on my office desk, in a stack of papers, and was incredibly fast and difficult to catch, with an agressive, random directional running pattern. I identified it through this website, with the help of a friend, and believe it is Castianeira descripta. Size is approx 15mm toe to toe. The gray / white spots on the spider's body are not visible in person, probably specular reflections from the very close flash of point and shoot in Macro mode.