Scutus unguis, common name the northern duck's bill, is a species of large sea snail or limpet, a marine gastropod mollusk in the family Fissurellidae, the keyhole limpets and slit limpets.

[1] The length of the shell attains 25.7 mm.

White shell, up to 6 cm long, distinctive by absence of slit or apical hole, though there is a small indent in the posterior margin.

The mantle has purple brown markings on a cream background.

(Richmond, 1997)[1] This marine species occurs in the Indo-west Pacific, from the Red Sea to the Solomon Islands; also off Papua New Guinea and Australia (Northern Territory, Queensland, Western Australia).