THE SKULL AS A WHOLE 145 



The orbit is small. Its margin is deficient behind in the dry skull, thick and rounded 

 in front and below. The cavity is limited below by a ridge on the frontal and 

 lacrimal bones, and is separated by a crest from the temporal fossa. The inner 

 wall is perforated above by the orbital opening of the supraorbital canal, and below 

 by the optic and ethmoidal foramina; on its antero-inferior part is the fossa in 

 which the inferior oblique muscle of the eye takes origin. Two lacrimal foramina 

 are found on or close to the anterior margin. The pterygo-palatine fossa is well 

 defined; its upper part forms a deep groove which leads from the large foramen 

 in the sphenoid (like that of the ox) to the very large maxillary foramen. The pre- 

 orbital region is deeply grooved in its length and is clearly marked oE by a ridge 

 from the nasal and frontal regions. The facial crest is short, usually thin-edged, 

 and lies above the fifth and sixth cheek teeth. A little (ca. 2 cm.) in front of it is 

 the infraorbital foramen. There is a ridged prominence over the canine alveolus. 

 In some skulls the anterior part of the upper jaw is inclined upward. 



The most striking features of the basal surface are as follows: The paramas- 

 toid processes are extremely long, less flattened than in the horse and ox, and nearly 

 vertical. At the inner side of the root of each is the hypoglossal foramen, and in 

 front of it are the stylo-mastoid foramen and a deep cavity in which the hyoid 

 process is concealed. The l:)ulla ossea is long, compressed laterally, and bears a 

 sharp, short, muscular process. The basioccij^ital is wide and flattened; it bears 

 a median crest and two lateral tuljercles. The posterior nares are small and are 

 wider below than above. On either side of them is the tuberosity of the palate 

 bone, and above this is the jiterygoid fossa. The palate is remarkably long and is 

 relatively narrow. It constitutes about two-thirds of the entire length of the skull. 

 It is widest between the canines and premolars and narrow at each end. It is 

 marked by a crest medially and by the palatine foramen and groove laterally. 

 The anterior part bears transverse ridges. It is moderately arched from side to 

 side. In some specimens it is nearly straight or slightly concave in its length; 

 in others it curves upward to a variable degree in front. The posterior end always 

 slopes upward more or less. 



The posterior or nuchal surface is remarkable for its height and the breadth 

 of the occipital crest. The central part above the foramen magnum is smooth and 

 concave from side to side, and is bounded laterally by ridges, which converge below 

 and end on two tubercles at the upper margin of the foramen magnum. The sur- 

 face is separated from the temporal fossae by the temporal crests, which curve 

 downward and outward and blend with the external auditory canals. The mastoid 

 process has the form of a plate which overlaps the root of the paramastoid process 

 and bears a crest on its anterior part. 



The cranial cavity is small, in spite of the great size of the cranium; the 

 discrepancy is due to the enormous development of the frontal sinuses in the adult. 

 It is relatively longer, but much lower than that of the ox. Its width is greatly 

 diminished between the orbits. The olfactory fossae are extensive and very oblicjue. 

 The floor resembles that of the ox, but the foramen ovale is absent, the dorsum 

 sellse is more developed, and the foramen lacerum basis cranii is like that of the 

 horse. Two oblique lateral crests clearly mark the limit between the cerebral and 

 cerebellar compartments. The tentorium osseum and the parieto-temporal canals 

 are absent. 



The nasal cavity is very long. Its posterior part is divided by a horizontal 

 plate into olfactory and respiratory parts. The olfactory part or fundus is above, 

 and contains the ethmoturbinals and ethmoidal meatuses. The lower part is 

 continuous with the inferior meatus and leads to the pharyngeal orifice; hence it is 

 sometimes called the naso-pharyngeal meatus. The bony roof is almost complete 

 in front on account of the great length of the nasal bones. 



The frontal sinus is a vast excavation in the adult animal. It involves all of 

 10 



