[Illustration: FIG. 7.—Side view of skull of Cape Jumping Hare (_Pedetes caffer_). × ⅗ _PMx_, Premaxilla; _Mx_, maxilla, _Ma_, jugal or malar; _Fr_, frontal; _L_, lachrymal; _Pa_, parietal; _Na_, nasal; _Sq_, squamosal; _Ty_, tympanic; _ExO_, exoccipital; _AS_, alisphenoid; _OS_, orbitosphenoid; _Per_, mastoid bulla.] Wedged in between the squamosal and the bones of the occipital and basisphenoidal region are the bones connected with the organ of hearing, known as the periotic and tympanic. The position of the periotic, which encloses the labyrinth or essential organ of hearing, is shown in Fig. 6. The periotic is divided into a very dense antero-internal moiety known as the petrosal, and a postero-external or mastoid portion (Fig. 8), which appears on the outer wall of the brain-case. The tympanic is produced horizontally outwards to form the external auditory meatus or tube of the ear, while the inner and under surface is frequently dilated into a shell-like auditory bulla (Fig. 8). The small bones of the internal ear known as the malleus, incus, and stapes are contained in the membranous _tympanic cavity_, which is situated in a space left among this group of bones. Further mention of these bones is made below under the head of the sense organs. In the Carnivora and some other groups the foramina on the base of the skull for the passage of blood-vessels and nerves are of considerable taxonomic importance. The position of the more important of these foramina is indicated in Fig. 8; but for details the reader may refer to the work on the _Osteology of the Mammalia_ already mentioned. Attention may, however, be particularly directed to the so-called alisphenoid canal, the position of which is shown in Fig. 8, since this is a feature of some importance in the classification of the Carnivora. This canal is a short channel running horizontally forward from near the foramen ovale through the alisphenoid, and opening anteriorly with the foramen rotundum; it is traversed by the external carotid artery. [Illustration: FIG. 8.—The right half of the hinder part of the base of the cranium of the Wolf (_Canis lupus_). _c_, Condyloid foramen; _l_, foramen lacerum posticum; _car_, carotid canal; _e_, eustachian canal; _o_, foramen ovale; _a_, posterior, and _a′_, anterior aperture of alisphenoid canal; _P_, paroccipital process of exoccipital; _m_, mastoid process of periotic; _am_, external auditory meatus; _g_, glenoid foramen, below which is the glenoid cavity for the condyle of the mandible. (Flower, _Proc. Zool. Soc._, 1869, p. 25.)]