White fork in the brown median stripe on carapace does not extend the full length of carapace, eliminating Pisaurina dubia.
Only two Tibellus have 4 spines on tibia I, T. duttoni and T. Chamberlini.
T. chamberlini has multiple pair of black spots on the abdomen. Eliminating T. chamberlini.
T duttoni has 1 or 2 pairs of black spots on the posterior 1/3 of the abdomen.
Also stipes on either side of median stripe appear to end near the back edge of the carapace.
Ref: Crab Spiders (Araneae Philodromidae Thomisidae) of Ramsey County Minnnesota Daniel T Jennings and Bruce Cutler 1996 pg. 11