Alcadia megastoma is a species of an operculate land snail, terrestrial gastropod mollusk in the family Helicinidae.

[1] (Original description) The shell is globose-conic, smooth, and shiny, with a rather thick yellowish-brown exterior.

The spire has very convex outlines and consists of four and a half slightly flattened whorls.

The outer lip is moderately reflected and thickened.

The columella and the adjacent part of the body whorl are bent into the plane of the aperture, with the columella forming a very minute tubercle.