About Megalobulimus popelairianus (Nyst, 1845)
This section describes the shell of Megalobulimus popelairianus. The shell is very large, solid, has an open umbilical cleft (rimate), and is shaped like an ovate cone. The spire tapers in a mostly consistent pattern, and the penultimate (second-to-last) whorl is slightly bulging. The last whorl is flattened on its dorsal side. The shell’s color is dark reddish-brown or deep chestnut, marked with narrow darker streaks, and has a lighter band along the margin just below the suture. The earliest whorls are dull reddish, while the apex is white. The entire shell surface is covered by a thick, shiny cuticle.
The nepionic (juvenile) shell is clearly defined, with 4 whorls. It is sculpted with strong, narrow radial riblets; these riblets become less distinct toward the lower suture on the fourth whorl. There are 2 additional whorls after the nepionic shell, which bear growth wrinkles and dense but somewhat irregular spiral granulation. This granulation fades on the last whorl, which instead has coarser sculpting from lengthwise wrinkles and usually more or less coarse spiral malleation. The sutures between whorls are deep, and the final suture is distinctly more oblique than the others.
The aperture makes up roughly half the total length of the shell, is trapezoidal in shape, and is white with a pale bluish-gray tint on the inside. The outer lip is distinctly reflected outward, is white or has a light brown edge, and curves outward in a convex shape. The columella is white, reflected, spreads onto the adjacent body whorl near its insertion, and extends as a thick white callus across the parietal wall. One or two low callous nodules are usually present near the upper end of this parietal callus.
Adult shells range from 85 to 98 mm in width, and 136 to 155 mm in height. The species is distributed in Ecuador and Brazil; its presence in Bolivia is considered doubtful.
