The skull of the Pigs (Figs. 103-105) has the axis of the face bent down upon the basicranial axis, as is also the case with the Sheep. Its most striking feature is the elevation and backward slope of the occipital crest formed by the union of the supraoccipital and parietals. The broad and flat frontals have small postorbital processes, which do not join the zygomata, so that the orbits are open behind. The nasals are very long and narrow; and the premaxillæ send up long nasal processes, stopping short of the frontals. A peculiar prenasal bone is developed at the anterior extremity of the mesethmoid, which serves to strengthen the cartilaginous snout. The palate is long and narrow, and extends behind the last molar tooth. In most species the occipital crest is more nearly vertical than in the skull represented in Fig. 104. [Illustration: FIG. 103.—Left lateral view of the dentition of the Boar (_Sus scrofa_), the roots of the teeth being exposed by removing the external lamina of bone.] [Illustration: FIG. 104.—Left lateral view of the skull of _Sus longirostris_. ⅕ natural size. (From Nehring.)] [Illustration: FIG. 105.—Frontal aspect of the cranium of _Sus longirostris_, ⅕ natural size. (From Nehring.)] This genus occurs at present under three principal modifications or subgenera. _A._—_Sus_ proper comprises a number of animals found in a wild state throughout the greater part of Europe (except where exterminated by human agency), the north of Africa, southern continental Asia, and the great islands of the Malayan archipelago, Formosa, and Japan. The following among others have been admitted by many zoologists as distinct species:—_Sus scrofa_, the Wild Boar of Europe, Asia Minor, and North Africa, once common throughout the British Isles; _S. sennaarensis_, North-East Africa; _S. cristatus_, India; _S. vittatus_, Java, Borneo, Amboyna, Batchian; _S. papuensis_, New Guinea; _S. timorensis_, Timor and Rotti; _S. andamanensis_, Andaman Islands; _S. taëvanus_, Formosa; _S. leucomystax_, Japan; _S. verrucosus_, Java, Borneo, Ceram; _S. barbatus_, Borneo; _S. celebensis_, Celebes, Philippines, and Moluccas; _S. longirostris_, Borneo and Java. The last four species form an allied group in which the facial portion of the skull may be greatly elongated; _S. barbatus_, and _S. celebensis_ being characterised by the small size and simple structure of the talon of the third molars. The skull of _S. longirostris_ is shown in Figs. 104 and 105. The small _S. andamanensis_ also has very simple third molars. _S. vittatus_, _S. leucomystax_, _S. cristatus_, _S. taëvanus_, and _S. papuensis_ form another group, in which the third molar is generally of very complex structure, more or less closely allied to the Wild Boar; and Dr. Nehring is inclined to think that the whole five might be included under a single specific name. This list will give some idea of the geographical distribution of wild Pigs, but it must be borne in mind that through