Nassodonta insignis

Nassodonta insignis is a brackish water snail, a gastropod mollusk in the family Nassariidae, equipped with gills and an operculum. It serves as the type species for the genus Nassodonta. This snail is found in shallow, brackish habitats along the southwest coast of India, and appears to be confined to that region.

It was reported from the Cochin (Kochi) backwaters near Ernakulam. Early confusion about its origin stemmed from a label reading “Pehoi river, China,” but later analysis showed that the associated genus Velorita (now Villorita cyprinoides) occurs only on the west side of the Indian Peninsula, near Cochin and the Kundapur river estuary, and never in China. “Pehoi” likely refers to a small village on the Malabar coast, and the “Peiho river” may actually be the Periyar River, the largest river feeding the Cochin backwaters.

Description

The shell reaches up to 12.0 mm in length, is ovate and solid, with some specimens broader than others. The teleoconch consists of only three to three and a half convex whorls, while the protoconch has one and a half embryonic whorls that are partly macroscopically axially striate. The shell is smooth except for very fine axial growth lines and a heavy, flat spiral cord at the base of the body whorl.

The aperture is moderately narrow, with a thickened outer lip that is not strongly variced; the interior bears four to five denticles that decrease in size toward the front. The columella is concave with a moderately broad and thick callus, a strong fold at the anterior end, and occasionally another weak plication. The siphonal notch is deep and broad, the parietal denticle is swollen, and the anal canal is distinct. Color ranges from fawn to brown, with the last whorl decorated by a moderately broad, interrupted brown subsutural band and a broad dark brown band on the posterior half.

The aperture is white but occasionally stained with brown. The operculum is thick and roundish, unusual for the family Nassariidae, and bears two vertical teeth. Smith correctly moved this species from the Buccinidae to the Nassariidae based on the multicuspidate rachidian tooth of the radula.