Definition of "umbones" []

• Plural form of umbo. (noun)

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• "[ARCA LIENOSA] lines of growth distinct, giving a striate appearance; the ligament area is marked by strong lines diverging from beneath the umbo; umbones distant; inside margin strongly sulcate or ribbed."
• "[ASTARTE CONCENTRICA] Shell small, thick, triangular, compressed, concentric; furrows close and regular; umbones acute, recurved; margin crenate."
• "The shell is orbicular, white, with depressed umbones, and the margins are either smooth or only finely crenulated; hinge teeth 2 -- 2, laterals 1 -- 1, muscular impressions rugose; anterior, elongated and within the pallial line; umbanal area with an oblique furrow."