Ilyanassa trivittata

Lore & Background

The shell of Ilyanassa trivittata is conic and acute, appearing yellowish-white. It is cancellate, giving it a granulated appearance with prominent, equidistant granules. Ten revolving impressed lines are present on the body whorl, along with a more conspicuous groove near the summit of each whorl. The spire is as long as or longer than the body, featuring a rufous revolving line near the suture. The body whorl is trilineate with rufous lines: one near the suture, one on the middle, and a third, rather darker, at the origin of the beak. The suture is regular and deeply impressed, and the beak is distinguished by a profound depression from the body whorl and is slightly reflected. The outer lip is not incrassated but has raised lines within upon the fauces that do not extend quite to the edge of the lip. The inner lip is distinctly lamellar, with an obsolete fold of the basal edge and a tooth near the superior junction with the outer lip.

Reader's Guide

Ilyanassa trivittata is a representative of the Nassariidae family, commonly referred to as Nassa mud snails or dog whelks. Its shell morphology, particularly the cancellate sculpture and the three rufous lines on the body whorl, provides a clear diagnostic feature for identification. The species is documented from the Northwest Atlantic Ocean, specifically off the coast of Canada in the Gulf of Saint Lawrence and the Bay of Fundy. The detailed original description of the shell—including the ten revolving impressed lines, the grooved summit, and the lamellar inner lip with its obsolete fold and tooth—contributes to the taxonomic understanding of this mud snail. While the species is not widely known outside malacological circles, its inclusion in standard references on aquatic invertebrates of the United States and Canada underscores its recognized place in the regional fauna. The mitogenomic phylogeny of mud snails in the genus Tritia has also involved this species, indicating its relevance to broader evolutionary studies within the Nassariidae.

Did You Know?

• The body whorl is trilineate with three rufous lines: one near the suture, one on the middle, and one at the origin of the beak.
• This species occurs in the Northwest Atlantic Ocean off Canada, including the Gulf of Saint Lawrence and the Bay of Fundy.