The skull of the alligator is very massive and has several peculiarities. 1. The bones of the dorsal surface are rough and pitted, especially in old animals. 2. The jaws are enormously large in proportion to the brain cavity, and are armed with many large teeth. 3. The mandibular articulation is some distance caudad to the occipital condyle. 4. The interorbital septum is mainly cartilaginous. 5. There is a complicated system of Eustachian passages connecting with the back of the mouth by a single opening. 6. The posterior nares are placed very far back and the palate is correspondingly long. The skull as a whole may be divided into three regions: the cranium, the lower jaw, and the hyoid; these will be described in the order given. _The Cranium._ As a matter of convenience the bones will be described as seen from the different aspects--dorsal, ventral, lateral, posterior, and in sagittal section--without particular regard to their grouping into segments or regions. _The Dorsal Aspect_ (Fig. 19). At the extreme posterior end of the median line lies the _parietal_ (23), double in the embryo but a single bone in the adult. It forms a part of the roof of the cranial cavity and articulates anteriorly with the frontal, laterally with the postfrontals, squamosals, and, according to Reynolds, with alisphenoids, pro-otics and epiotics, and ventrally with the supraoccipital. It forms the median boundary of each of the two _supratemporal fossæ_ (sf). On each side of the parietal and forming the posterior comers of the rectangular postero-dorsal region of the skull are the _squamosals_ (7). Each squamosal articulates medially with the parietal, anteriorly with the postfrontal, and ventrally with the quadrate and exoccipital. It forms part of the posterior and lateral boundaries of the supratemporal fossa and a part of the roof of the external auditory meatus. Articulating with the anterior border of the squamosals and forming the anterior corners of the rectangular region mentioned above are the _postfrontals_ (6). The postfrontal articulates medially with the parietal and frontal, and ventrally with the alisphenoid and a small part of the quadrate. It sends, in a ventro-lateral direction, a thick process that unites with a similar process from the jugal to form the _postorbital bar_ (pb) which lies between the orbit (o) and the temporal fossa (tf). The postfrontal forms the antero-lateral boundary of the supratemporal fossa.