Artiodactyla. The skull in Artiodactyla differs from that in Perissodactyla in the fact that the posterior end of the nasal is not expanded and there is no alisphenoid canal.

The skulls in the different groups of Artiodactyla differ considerably from one another.

Fig. 94. A, Cranium and B, mandible of a Pig (Sus scrofa) × 1/5.

(Camb. Mus.)

1. jugal.11. anterior palatine foramen.
2. postorbital process of the12. palatal plate of maxillae.
frontal.13. coronoid process.
3. zygomatic process of the14. mandibular condyle.
squamosal.i 1, i 2, i 3. first, second, and third
4. supra-occipital.incisors.
5. glenoid cavity.c. canine.
6. occipital condyle.pm 1, pm 2, pm 3, pm 4. first,
7. foramen magnum.second, third, and fourth
8. paroccipital process of thepremolars.
exoccipital.m 1, m 2, m 3. first, second, and
9. tympanic bulla.third molars.
10. pterygoid.

The skull of the Pig[166] will be described as illustrative of the skull in the Suina. In the Pig as in most Artiodactyla the face is bent sharply down on the basicranial axis, the commencement of the vomer being situated below the mesethmoid instead of in front of it as in most skulls. The occipital region of the skull is small, and the line of junction of the supra-occipital and parietals is raised into a prominent occipital crest. The parietal completely fuses at an early stage with its fellow, and the exoccipital is drawn out into a long paroccipital process (fig. 94, A, 8). The frontal is large and broad and drawn out into a small postorbital process. The lachrymal too is large and takes a considerable part in forming the side of the face in front of the orbit, as does also the jugal, though to a less extent. The face is long and tapers much anteriorly. The nasals are long and narrow, as are the nasal processes of the premaxillae, which do not however reach the frontals. A prenasal ossicle is developed in front of the mesethmoid. The palate is long and narrow, the pterygoid (fig. 94, A, 10) is small, but the pterygoid process of the alisphenoid is prominent. The squamosal is small and has the tympanic fused with it; the tympanic is dilated below, forming a bulla (fig. 94, A, 9) filled with cancellous bone, and above forms the floor of a long upwardly-directed auditory meatus. The mandible has a high ascending portion and a small coronoid process (fig. 94, B, 13). The hyoid differs from that of most Ungulates, the stylo-hyal being very imperfectly ossified.

Fig. 95. Mandible of a Hippopotamus (H. amphibius) × 1/7.