Amblypoda. In the Uintatheriidae (Dinocerata) the skull has a very remarkable character, being long and narrow and drawn out into three pairs of rounded protuberances, a small pair on the nasals, a larger pair on the maxillae in front of the orbits, and the largest pair on the parietals. The cranial cavity, and especially the cerebral fossa, is extraordinarily small. The orbit is not divided behind from the temporal fossa. The mandible has a prominent angle, and a long curved coronoid process; its symphysial portion bears a curious flattened outgrowth to protect the great upper canines.

In Coryphodon the skull is of a more normal character, being without the conspicuous protuberances. The cranial cavity though very small is not so small as in Uintatherium.

Fig. 96. Skull of a young Indian Elephant (Elephas indicus), SEEN

from the right side, the roots of the teeth have been exposed. × 1/8. (Camb. Mus.).

1. exoccipital.14. postorbital process of the
2. parietal.frontal.
3. frontal.15. lachrymal.
4. squamosal.16. pterygoid process of the
5. jugal.alisphenoid.
6. premaxillae.i 1. incisor.
7. maxillae.mm 3., mm 4. third and fourth
9. supra-occipital.milk molars.
13. basi-occipital.m 1. first molar.

Proboscidea. The character of the skull in the young elephant differs much from that in the old animal. In very young individuals the skull is of a normal character, and the cranial cavity is distinctly large in proportion to the bulk of the skull. But as the animal gets older, while its brain does not grow much, the size of its trunk and especially of its tusks increases greatly; and consequently the skull wall is required to be of very great superficial extent in order to afford space for the attachment of the muscles necessary for the support of these heavy weights. This increase in superficial extent is brought about without much increase in weight of bone by the development of an enormous number of air cells in nearly all the bones of the skull; sometimes, as in the case of the frontal, separating the inner wall of the bone from the outer, by as much as a foot. This development of air cells is accompanied by the obliteration of the sutures between the various bones. The most noticeable point with regard to the cranial cavity is the comparatively large size of the olfactory fossa. The supra-occipital (figs. 96 and 97, 9) is large—exceedingly large in the adult skull; the parietals (figs. 96 and 97, 2) are also very large. The frontals send out small postorbital processes, but these do not meet processes from the small jugal, which forms only the middle part of the slender zygomatic arch, the anterior part being formed by the maxillae. The lachrymal (fig. 96, 15) is small and lies almost entirely inside the orbit. The anterior narial aperture (fig. 97, 8) is wide and directed upwards, opening high on the anterior surface of the skull. It is bounded above by the short thick nasals and below by the premaxillae. The narial passage is freely open, maxillo-turbinals not being developed. The palatine is well developed, the pterygoid is small and early fuses with the pterygoid process of the alisphenoid. The tympanic is united with the periotic but not with the squamosal, and forms a large auditory bulla. There are no paroccipital or postglenoid processes. The exoccipital is not perforated by the condylar foramen,—a very exceptional condition.