Maxxis Hookworm Tires I recently purchased two Maxxis Hookworm street tires. There are no rotation arrows on them. Does this mean it doesn't matter how they are mounted on the wheel?
These are slick tires, so it doesn't really matter. Even if there are rotation marks, they generally have minimal/trivial differences in performance if any on slick road tires for direction of rotation. 

For tread for things like mountain bike tires, the performance may be different depending on the tread orientation, with how much the tread grabs depending on the way the rotation.