1. relating to or resembling an umbo, especially the beak-like projection on a bivalve shell
Usage: biological; technical

Examples

• The umbonal region of the clam shell showed signs of erosion.
• Researchers examined the umbonal cavity for growth patterns.
• The umbonal area is often the oldest part of a mollusk shell.
• Distinctive umbonal ridges helped identify the species.
• The umbonal sculpture varied between different bivalve specimens.