About Prisogaster niger (W.Wood, 1828)
The shell of Prisogaster niger ranges in size from 10 mm to 35 mm. It is very solid, imperforate, and has an ovate shape. Its color is a deep, dull purplish or bluish black. The short spire is convex and blunt. There are 5 to 6 whorls, which are somewhat flattened below the sutures. They have a superficial spiral line, and are marked with light incremental striae. The large aperture is very oblique and ovate, is silvery on the inside, and rounded at the lower end. The outer lip is slightly fluted on the inside. The wide white columella bears a longitudinal rib on its face that rises in the umbilicus region. The parietal wall is eroded and white; it is either smooth, or marked with three white transverse rugae. The oval operculum is concave on the inside, is buff-colored, and has 2 to 3 very rapidly increasing whorls. The nucleus is positioned one-fourth of the total distance across the operculum’s face from the basal margin. The outer surface of the operculum is white, very convex, and has indistinct obsolete rugosity. This species occurs in the Pacific Ocean, ranging from Peru to the Strait of Magellan.
