A portion of the floor of the orbit and the opening of the lachrymal canal (_o_) may also be seen in dorsal view; they are described in connection with the lateral surface.
The =caudal surface= of the skull is formed largely by the occipital bone (Fig. 17), surrounding the foramen magnum (Fig. 17, _d_). At the sides of the foramen magnum are the two prominent curved occipital condyles (_e_) for articulation with the atlas. Craniolaterad of the condyles, separated from them by a deep notch, are the jugular processes (_f_) of the occipital, closely applied to the caudal ends of the tympanic bullæ.
Dorsad of the foramen magnum are faint indications of a median ridge running dorsad, the =external occipital crest= (Fig. 17, _i_); this rises at its junction with the lambdoidal ridge to form the prominent =external occipital tubercle= (Fig. 39, _b_). The dorsal and dorsolateral boundaries of the posterior surface are formed by the lambdoidal ridge (Fig. 17, _h_; Fig. 39, _a_).
The =lateral surface= of the skull (Fig. 40) is much more complicated than the dorsal and posterior surfaces. Caudally the occipital condyles (_a_) and external occipital crest (_b_) are visible; dorsocaudad the sagittal crest (_c_).
Extending from the caudal end of the sagittal crest the lambdoidal ridge (_d_) is seen passing ventrocraniad to the tympanic bulla, thence craniad to the root of the zygomatic arch. In the ventral part of the caudal region the tympanic bulla (_e_) is visible with the jugular process (_f_) of the occipital pressed close against its caudal end. Just craniad of the jugular process the mastoid process (_g_) of the temporal rests against the side of the bulla. Beneath the cranial edge of this process is the opening of the stylomastoid foramen (_h_) for the seventh nerve, while just ventrad of the foramen is the small pit (_i_) in the tympanic bulla for the reception of the tympanohyal bone. Craniad of the stylomastoid foramen is the large opening of the external auditory meatus (_j_), leading into the middle ear.
Immediately dorsocraniad of the external auditory meatus the zygomatic arch begins as the zygomatic process (_k_) of the temporal bone. On the cranial surface of the base of this process is the deep mandibular fossa (_l_) for the condyle of the mandible. This fossa is bounded caudally by the prominent postmandibular process (_m_).