hypoplastron

from The Century Dictionary.

• noun The third lateral piece of the plastron of a turtle: applied by Huxley (“Anat. Vert.,” p. 174) to what others call hyposternum. See second cut under Chelonia.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Anat.) The third lateral plate in the plastron of turtles; -- called also hyposternum.

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

• noun anatomy The third lateral plate in the plastron of turtles.