Hesperarion plumbeus Roth, 2004  

External: Mantle ~30% of body length; unicolor gray body, with lighter sides and neck and slight dark mottling on mantle; skin grooves slightly darkened; keel present; foot fringe light tan to gray, without strong stripes; light tan sole; caudal mucus pore present (Roth 2004).

Internal: Short penis, broader toward apex, and with internal teardrop-shaped verge; penial retractor on first bend of epiphallus; appendix next to free oviduct on atrium; long spermatheca duct, broader for first half of length than the second half; small, acorn-shaped spermatheca (Roth 2004).

Differs from H. niger, because penis is shorter and has a teardrop-shaped rather than conical verge (Roth 2004). .