The =quadrate= (figs. 43, A, 13 and 44, 8) of each side is a large somewhat flattened bone firmly fixed in among the other bones of the skull. It is terminated posteriorly by an elongated slightly convex surface, coated with cartilage in the fresh skull, by which the mandible articulates with the cranium. The dorsal surface of the quadrate is flat behind, further forwards it becomes much roughened and articulates with the exoccipital and squamosal; further forwards still it becomes marked by a deep groove which forms the floor of the external auditory meatus and part of the tympanic cavity. The anterior boundary of the quadrate is extremely irregular, it is united dorsally with the postfrontal, pro-otic, and squamosal, and more ventrally with the alisphenoid. The smooth ventral surface looks into the pterygoid fossa. In front the quadrate forms the posterior boundary of the supratemporal fossa and foramen ovale, and is continuous with the alisphenoid, while it sends down a thin plate meeting the pterygoid and basisphenoid. On the inner side of the dorsal surface of the quadrate near the condyle, is a small foramen which leads into a tube communicating with the tympanic cavity, by a foramen lying in front of and ventral to that for the exit of the facial nerve. By this tube air can pass from the tympanic cavity into the articular bone of the mandible. The _squamosal_ (fig. 44, 7) meets the quadrate and exoccipital below, and forms part of the roof of the external auditory meatus, while above it forms part of the roof of the skull and has a pitted structure like that of the other bones of the roof. It is continuous with the postfrontal in front, forming with it the =supratemporal arcade= which constitutes the outer boundary of the supratemporal fossa. It meets also the parietal on its inner side, forming the =post-temporal bar=, the posterior boundary of the supratemporal fossa. It may be useful to recapitulate the large vacuities in the surface of the Crocodile's cranium. _Dorsal surface._ 1. =The Supratemporal fossae=. Each is bounded internally by the parietal, behind by the =post-temporal bar= formed by the parietal and squamosal, and externally by the =supratemporal arcade= formed by the squamosal and postfrontal. The postfrontal meets the parietal in front and forms the anterior boundary of the supratemporal fossa. 2. The =Lateral temporal= or =infratemporal fossae=. These lie below and to the outer side of the supratemporal fossae. Each is bounded dorso-internally by the supratemporal arcade; and behind by a continuation of the post-temporal bar formed by the quadrate and quadratojugal. The external boundary is the =infratemporal arcade= formed of the quadratojugal and jugal, while in front the fossa is separated from the orbit by the =postorbital bar= formed by the junction of outgrowths from the postfrontal and jugal.