columella

noun

1. Any of various small structures in plants or animals that are columnar in shape.
2. The skin at the end of the septum which separates the nostrils.
3. (comparative anatomy) In birds, reptiles, and amphibians, the small bone which carries vibration from the tympanum to the inner ear.
4. In gastropods, the structure at the center of the whorls of the shell.