Vertigo Milium - Shell Description

Shell Description

The shell is small, subcylindrical, smooth shining. Growth lines are very fine, a little oblique. Apex is smooth. The color of the shell is dark chest-nut. The shell has 5 rounded whorls, that are somewhat regularly increasing and decreasing to a bluntly rounded apex. Sutures are impressed.

The aperture is obscurely semicircular, lateral and truncated above. The "circumference" of the aperture is "made up of two curves of different radius uniting in the peristome, where the junction causes an angle projecting inwards, the smaller curve comprising about one-fourth part and forming the superior portion of the peristome. The aperture has six teeth as follows: two sharp, projecting teeth of about equal size placed on the parietal wall and dividing that region into three nearly equal parts; one on the columella, large, massive, broad; a third placed on the outer lip above or at the junction of the two radii, long, curved, ridge-like, pointing directly between the two parietal teeth; a fourth on the base of the lip, small, conical, tubercular; and one large, entering, elevated, long lamina, which begins on the base of the lip and curves backward until it disappears behind the columella tooth (this is the "gular lamina" of Sterki). Peristome is white or brownish-white, reflected, the terminations separated, but joined by a prominent callus. The umbilicus is well marked, open, deep. Base of the shell is rounded.

The width of the shell is 0.80-0.90 mm. The height of the shell is 0.90-1.40 mm. The height of aperture is 0.25-0.30 mm.