Page:The Osteology of the Reptiles.pdf/101

Rh the extent of the elevated facial carina in front of the nares, and the shape of the teeth, more slender and cylindrical in those with slender jaws, more flattened and compressed in those with a compressed and elevated face, doubtless because of the more dominant fish-eating habits of the former, the more general carnivorous habits of the latter.

The skull of the Crocodilia invariably lacks the postfrontals, supratemporals, epipterygoids, tabulars, septomaxillae, and parietal foramen, and the paroccipital is fused with the exoccipital. The parietals and frontals are fused in the midline. The supraoccipital is a triangular bone, excluded from the foramen magnum. The quadratojugals take part in the formation of the lateral temporal opening, narrow bones between the quadrates and jugals extending forward to meet the postorbitals. The quadrates are firmly wedged in between the quadratojugals, postorbitals, parietals, exoparoccipitals, postoptics, squamosals, proötics, basisphenoid, and pterygoids, an extensive connection. The supratemporal openings are large in the early forms, small in the later ones, and almost [or entirely] obsolete in some. The lateral temporal opening is separated in the teleosaurs from the orbits by an unmodified postorbital bar immediately below the skin. In the broader-faced amphicoelian and in all the procoelian types it is a cylindrical bar with a considerable space between it and the skin. The postoptics (Fig. 69, as) are fully ossified, extending from the basisphenoid to the frontals. There is no ossified interorbital septum. An antorbital vacuity is often present in the teleosaurs, but only rarely has been found in the early procoelian types. The nasals may or may not separate the external nares, connecting with the premaxillae; they are divided by a cartilaginous septum in life. The nares are always at the extremity of the face, no matter how long and slender it may be. There is a eustachian canal connecting with the otic sinuses, in the median line between the basioccipital and basisphenoid.

The most important modifications of the crocodilian skull are found in the palate, distinguishing these reptiles from all others. The maxillae meet broadly in the middle line, excluding the prevomers