Rod Crawford identified this spider genus as Bassaniana, a bark crab spider, and suggested it is either Coriarachne brunneipes or Bassaniana utahensis. He said "You tell them apart by whether the main carapace spines are blunt/clubbed (utahensis) or pointed (brunneipes)." It was found under a shed roof in a box.The shed is located on a valley floor - elevation approximately 900' Seems to be a cold hardy species. Thanks!