I recently dissected this specimen from the Strickland Museum (University of Alberta). It was collected by Danny Shpeley and George Ball in 1977 on a collecting trip in the NWT. It is the largest Corticaria that I have come across and has quite distinct external morphology. The pronotal margins are hardly toothed, and there is not an obvious post-basal fovea. The 5th sternite (see photo) is emarginated medially in the male.
Determination confirmed by W. Rucker.