. Bulletin. Natural history. 52 PEABODY MUSEUM BULLETIN 23 Its articular face is nearly circular in Ectenosaunis, though in Clidastcs, Mosa- saiu'iis, Platecarpus, Halisaurus platyspondylus, Prognathodon and Tylosaurus it is more laterally compressed. The internal wing of the splenial is small and widely separated from the coronoid in Platecarpus and Tylosaurus. It is larger in Prognathodon, but is overlapped above by a descending wing of the coronoid. In Clidastcs the internal wing of the angular is very well developed and may contact the coronoid dorsally. The angular of Plotosaiirus spreads
. Bulletin. Natural history. 52 PEABODY MUSEUM BULLETIN 23 Its articular face is nearly circular in Ectenosaunis, though in Clidastcs, Mosa- saiu'iis, Platecarpus, Halisaurus platyspondylus, Prognathodon and Tylosaurus it is more laterally compressed. The internal wing of the splenial is small and widely separated from the coronoid in Platecarpus and Tylosaurus. It is larger in Prognathodon, but is overlapped above by a descending wing of the coronoid. In Clidastcs the internal wing of the angular is very well developed and may contact the coronoid dorsally. The angular of Plotosaiirus spreads posteriorly over much of the ventromedial surface of the articular. The angular branch of the mandibular nei-ve emerged through a foramen in Clidastcs, Mosasaurus, and Halisaurus platyspondyhis, and through either a foramen or a notch in Tylo>- saurus and Platecarpus (?). SURANGULAR The surangidar is essentially an elongated rectangular piece of bone with a tongue projecting posterodorsally over the lateral surface of the articular to end in a rounded point, usually near the posteroexternal corner of the glenoid fossa. The dorsal surface of the tongue is convex from side to side and forms the lateral boundary of the glenoid fossa. This part of the articulating surface widens anteriorly, finally curving medially behind a transverse ridge of bone that marks the anterior limit of the fossa. The lateral exit for the cutaneous. Text-fig. 29. Medial view of mandible of Platecarpus iciericus (AMNH 1821, X %). branch of the mandibular nerve lies under the anteroexternal comer of the glenoid fossa. Beneath this foramen a rounded crest of bone descends ventroante- riorly, curving to parallel the horizontal axis of the surangular anteriorly and fi- nally merging with the lateral surface of the bone below the posterior boundary of the coronoid suture. The pars superficialis and medialis of the M. adductor mandibulae externus insert along an identical crest in Varanus. Above this crest
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