Natica cymba Menke, 1828 Sigaretus maximus Philippi, 1844 Sinum cymba, common name the concave ear moon snail, is a species of predatory sea snail, a marine gastropod mollusk in the family Naticidae, the moon snails.

[1] It was classified by the German malacologist Karl Theodor Menke in 1828 with the name Natica cymba.

Shell with a wide opening, brown and smooth; with an external coloration of purplish-brown to pale, gray or white, on a surface with a waxy shine, provided with fine spiral lines.

The spiral is low and up to 7 centimeters long, when developed; ending in a broad turn.

It is common in the eastern Pacific Ocean, on the coasts of South America to Chile, including the Galápagos, and southern Central America,in Panama.