sublingua

from The Century Dictionary.

• noun A process of the mucous membrane of the floor of the mouth developed between the tip of the tongue and the symphysis of the lower jaw of some animals, as lemurs: it may acquire considerable size, and become denticulated or pectinated.

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

• noun (Anat.) A process or fold below the tongue in some animals.

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

• noun anatomy A muscular secondary tongue found below the primary tongue in prosimian primates.