Simnialena uniplicata, common name the one-tooth simnia, is a species of sea snail, a marine gastropod mollusk in the family Ovulidae, the ovulids, cowry allies or false cowries.

The shell of is shiny and smooth, and the shape of an elongated egg, with a flat base which shows a long, narrow, slit-like aperture.

[2] Simnialena uniplicata occurs in shallow water on the eastern coast of the United States, Colombia, Jamaica and Brazil.

[3] Minimum recorded depth is 0 m.[2] Maximum recorded depth is 116 m.[2] Simnialena uniplicata has a symbiotic relationship with the sea whip Leptogorgia virgulata on which it lives.

The snail's white colour is derived from the pigments it absorbs and which it incorporates into its shell after eating debris from the coral.