xiphisternal

from The Century Dictionary.

• In anatomy, of the nature of the xiphisternum, or last sterneber of the sternum; pertaining to the xiphisternum; ensiform or xiphoid, as a cartilage or bone of the breast-bone.
• In Chelonia, xiphiplastral. See cuts under Chelonia and plastron.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective of, or relating to the xiphisternum