The helix is the prominent rim of the auricle. Where the helix turns downwards posteriorly, a small tubercle is sometimes seen, namely the auricular tubercle of Darwin.

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  The muscles of the auricula.
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  Left: Darwin's tubercle. Right: the homologous point in a macaque.
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  External ear. Right auricle. Lateral view.
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  External ear. Right auricle. Lateral view.
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  External ear. Right auricle. Lateral view.

This article incorporates text in the public domain from page 1033 of the 20th edition of Gray's Anatomy (1918)