The fused dentaries (fig. 38, 12) form by far the largest of the bones; they constitute the flattened anterior part of the mandible, and extend back below the other bones almost to the end of the jaw.
The coronoid is the most anterior of the paired bones, it forms a prominent process to which the muscles for closing the jaw are attached.
The articular (fig. 38, 11) is expanded, and with the supra-angular forms the concave articulating surface for the quadrate.
The splenial (fig. 38, 10) is a thin plate applied to the inner surface of the posterior part of the mandible.
The angular (fig. 38, 13) is a slender plate of bone lying below the supra-angular and splenial.
(3) The Hyoid.
The hyoid apparatus is well developed, parts of the first two branchial arches being found, as well as of the hyoid proper. It consists of a more or less oblong flattened basilingual plate or body of the hyoid which represents the fused ventral ends of the hyoid and branchial arches of the embryo, and is drawn out into a point anteriorly. The greater part is formed of unossified cartilage, but at the posterior end it is bilobed, and a pair of ossified tracts occur. To its sides are attached three pairs of structures, which are portions of the hyoid and first and second branchial arches respectively.
The free part of the hyoid consists of a small piece of cartilage attached to the anterior part of the basilingual plate at its widest portion (fig. 53, 2).
The anterior cornu or free part of the first branchial arch is much the largest of the three structures. Its proximal portion adjoining the basilingual plate is cartilaginous, as is its distal end; the main part is however ossified.
The posterior cornu or free part of the second branchial arch (fig. 53, 4) consists of a short flattened cartilaginous bar arising from the bilobed posterior end of the basilingual plate.