Os, (from v, and Hyoides 4368 because formed like the Greek letter upsilon,) yoides, hypsiloides, and upsiloides; bicorne, and lambdoides. It is situated in an horizontal position between the root of the tongue and the larynx; convex on its anterior part, and hollow on the posterior: the cornua become smaller as they run back, and diverge a little; at the end of each cornu is a graniform appendicle, from whence a ligament runs to the styloid process of the os temporis, and another ligament connects the bone to the larynx. These ligaments are sometimes in part or wholly osseous, and the os hyoides is joined to the temporal bone by anchylosis. In the foetus it is almost wholly cartilaginous, only a small osseous point appearing in the middle of its body and in each of its cornua. The appendicles are not observable at birth, and remain cartilaginous for many years, it is the basis and support of the tongue, and the muscles of the larynx and fauces.