In this case the shell is said to be umbilicated, and the opening referred to is the umbilicus.
Each of these lenses is umbilicated, or marked with a central depression.
A generic division of the species composing Ranella, characterized as having the shell not umbilicated.
The shell is described as heliciform, umbilicated, transparent, with the aperture transverse.
Shell flattened, umbilicated; foot anteriorly truncated with angles produced into lobes.