This individual's plates are so eroded I don't want to venture a guess on which species it is.
9-mile Point, Sechelt Inlet, British Columbia. Max depth 24m.
Eric's Pinnacle, Dammit (EPD) site. Pacific Grove, Monterey Bay. Max depth 18 m
Dive in Monterey bay, west of Pt. Pinos. Max depth 55 ft/17 m.
Not sure if this is Stenoplax heathiana or a juvenile S. conspicua.