What is (a) A depression or opening in the center of the base of many spiral shells. (b) Either one of the two apertures in the calamus of a feather called?
umbilicus — (Zoöl.) (a) A depression or opening in the center of the base of many spiral shells. (b) Either one of the two apertures in the calamus of a feather. (Webster's 1913.)
Sources
- Webster's Unabridged Dictionary, 1913 edition (public domain, via GCIDE / Project Gutenberg).
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- Published: 2026-07-17 · Modified: 2026-07-17