As Adamnestia modesta:
Distinctive features are 1) cylindrical, involute, robust shell attaining 11 mm in height, 2) proto-conch immersed, 3) spire sunken within the deep adapical umbilicus, which is bounded by a rounded angulation, 4) aperture as high as the total height, narrow and with parallel margins in the upper three-fourths, wider and ovate-triangular in the abapical one-fourth; outer lip thin; inner lip thinly calloused, with weak, quickly ascending columellar fold, 5) body whorl with fine, wavy spiral lines that tend to be obsolete in the middle and are somewhat stronger abapically. The subrounded rim of the adapical umbilicus suggests assignment to the genus Adamnestia Iredale, 1936. Cylichna sibogae Schepman, 1913, is closely similar, but has a more slender shell with the adapical umbilicus bounded by a sharp angulation. It is of note that Cylichna braunsi Yokoyama, 1920, type species of the genus Eocylichna Kuroda & Habe, 1952, was regarded by SHUTO (1969) as a synonym of Schepman's taxon.
DISTRIBUTION AND HABITAT. The species occurs in the Southwest Pacific. It is a sublittoral element dwelling in muddy or fine sandy bottoms. Previous records in the Gulf of Thailand refer to beached shells (SWENNEN et al., 2001). FOSSIL RECORDS. Holocene of Thailand.