Sagda alligans is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Sagdidae.
The shell is imperforate, globosely conoidal, white, under a brownish-yellow epidermis. The incremental striae are regular, stronger on the spire than on the body whorl. The number of whorls is 8. The shell has a narrow, aperture with a deep-seated strong basal lamella.
The adult shell diameter is 15âÂÂ20 mm.
This species occurs in Jamaica.