Bullia digitalis

Background

The shell of Bullia digitalis is narrow, smooth, and elongated, with a long pointed spire and seven hardly convex whorls. It is reddish yellow in color, with a simple, shallow suture and a moderately pointed apex. The aperture is ovate, smooth, widened at the middle, and strongly emarginated at the base.

The columella is yellowish, smooth, and arched, and a keel runs from the upper third of the aperture to the base of the outer lip, with oblique folds filling the space between the keel and the lip edge. The outer lip is simple, thin, sharp, and slightly effuse towards the middle. The large oval foot is off-white, and the operculum has serrated margins.

When the tide rises, the snail emerges from the sand, spreads its large foot like a sail, and surfs up the beach in response to the smell of carrion. It uses its proboscis to suck soft tissues from prey, often gathering in large numbers to feed on dead and stranded jellyfish and bluebottles. At low tide, it burrows back into the sand. Similar species on the southern African coast include Bullia rhodostoma and Bullia natalensis (pleated plough shell), but B. digitalis lacks pleated whorls; all common plough shells are differentiated only by color.