Megalomastoma (Tomocyclus) Crosse & P. Fischer, 1872 Tomocyclus is a genus of land snails, terrestrial gastropod mollusks in the subfamily Megalomastomatinae of the family Megalomastomatidae.

[1] (Original description in Latin) The shell is perforated, turreted, and truncated.

The upper margin of the outer lip is interrupted, with a unique, incised, and hollowed-out appearance.

The operculum is circular, corneous but relatively thick, and spirally wound.

It is slightly flattened anteriorly and reinforced posteriorly by a blunt, rounded process.