[Footnote L: _Fauna der Vorwelt. Reptilien aus dem Lithographischen schiefer._ Frankfurt am Main. 1859. pp. 15-23.]
The skull of the Pterodactyle can only be compared with those of birds and lizards. The form is essentially Avian, and the sutures are indistinct or obliterated as in birds, while in reptiles they are persistent The temporal bone enters into the formation of the reservoir for the brain, which is eminently characteristic of birds and quite different from anything found in lizards. The snout resembles a bird in being chiefly formed by the intermaxillary bone, which bounds the front of the anterior nares; and, as in birds, the bone extends backward between the eye-cavities to the frontal bone. The corresponding intermaxillary ridge of the Monitor is of less extent.
The frontal-bone forms the highest part of the skull, and is similar to that of birds. The principal frontal is double, and forms the upper and hind part of the cavity for the eye, and covered the greater part of the large brain, composed of two hemispheres, in which Oken long ago saw a similarity to the higher animals. The arched form of the back part of the skull is bird-like. The double parietal adjoins the principal frontal, and is conditioned like the parietal in birds. The supra-occipital is single as in birds, expanded, and forms the part of the skull which extends furthest back. From the form of the back part of the skull it may be concluded that the foramen magnum was situated as in birds, and that the head and neck were moved as in birds, and not as in reptiles and mammals.
The temporal bone rests upon the parietal and frontal, and forms much of the temporal foss. Its anterior border does not appear to enter into the margin of the orbital cavity as in birds, but seems to be replaced by the post-frontal, which resembles that of the Chameleon. Its hindmost branch, which can hardly be supposed to be the jugal, forms the outer boundary of the temporal foss by uniting with a process which is probably part of the mastoid. A similar closing of the cavity for the temporal muscles is also to be found in birds. The jugal and maxillary do not follow the bird type. The jugal consists of a single bone which forms the greater part of the anterior and inferior boundary of the cavity of the eye, which is surrounded with bones, as in Dragons and Iguana. In those birds in which the cavity of the eye is surrounded with bones the jugal does not enter into it. As in lizards, at its upper end the jugal is commonly connected with the lachrymal, which bone is like that of a bird. A bone, which appears to be the pre-frontal, enters into the back of the nasal aperture.