Christmas Fern – Polystichum acrostichoides

The radial notch of the ulna (lesser sigmoid cavity) is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius.

It is concave from before backward, and its prominent extremities serve for the attachment of the annular ligament.

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  Annular ligament of radius, from above.

This article incorporates text in the public domain from page 215 of the 20th edition of Gray's Anatomy (1918)

• Right ulna (anterior - proximal end)^{[dead link]} - BioWeb at University of Wisconsin System
• elbow/elbowbones/bones3 at the Dartmouth Medical School's Department of Anatomy