Amastra cornea was a species of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Amastridae.
(Original description) The shell is irregularly acutely conical with a pointed apex and an inflated body whorl. It is thin and corneous, adorned with minute longitudinal striations. Comprising seven rounded whorls, the shell features a subovate aperture with a thin, translucent lip. The columella is straight, white, and equipped with a transverse, plaited tooth.
The shell's coloration is a uniform dark horn, contrasting with the white columella and tooth. [1]
This extinct species was endemic to Oʻahu, and was known from around Waialua.