Hesperarion mariae Branson, 1991
External: Light red-gray body and mantle; lighter sides; darker head and neck; large, irregular black spots and marks on mantle; little black spots that may form lines along skin grooves; mantle forms a hump over internal shell; light and dark stripes on foot fringe; large, downward-bent caudal mucus pit; slightly 3-part, white sole (Branson 1991; Roth 2004).
Internal: Asymmetric internal shell; cylindrical penis with a large conical verge in the apex; large, thin-walled dart sac with one long, curved dart in the atrium; oviduct significantly longer than penis (Branson 1991; Roth 2004).
To 30 mm long (Roth 2004); preserved: 20 mm long, 4 mm wide, mantle 7 mm long (Branson 1991).
Oregon (Tillamook Co., Lane Co., Douglas Co.) (Roth 2004).
Some specimens were found under leaf litter in a spruce forest at the type locality (Roth 2004).