The umbilical perforation is oval and about 5 mm long and 3 mm wide. The umbilical walls are steep and the umbilical shoulders are subangular. The umbilical nodes are thickenings of the test and thus are not visible on the internal mold of all but the largest specimens and they may be easily destroyed by abrasion of the shell. The umbilical nodes become more and more obliquely elongated as the conch grows and on the living chambers of mature individuals are up to 6 mm long and 2-4 mm high. Each growth line forms a broad, moderately deep, rounded, ventral sinus and on each side of it, a broad, low, gently rounded, lateral salient.
Growth lines are essentially straight and directly transverse on the umbilical walls.
The adapical portions of the conch are smooth or nearly so, but near the midpoint of the second volution transverse lateral plicae develop. The ventral and dorsal ends become the ventrolateral and umbilical nodes respectively, whereas the center portion is lost. The ventrolateral nodes increase in size as the size of the conch increases. Near the middle of the second volution two rows of similar nodes are gradually developed on the venter. These nodes continue to enlarge and to become progressively less longitudinally elongated and more conical with growth.