keyhole urchin

English

Noun

keyhole urchin (plural keyhole urchins)

1. Any of numerous clypeastroid sea urchins (sand dollars) of the genus Melitta

   Synonym: keyhole sand dollar

2. (dated) Any of various notched sand dollars of genera Rotula and Encope.

Derived terms

• five-holed keyhole urchin
• six-holed keyhole urchin

References

• “keyhole”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.