BONES OF THE FACE 139 



noid. The edge behind this foramen articulates with the orbital wing of the sphe- 

 noid, not the frontal, as in the horse. 



The pterygoid bone is wider than in the horse, and forms the greater part of the 

 lateral boundarj^ of the posterior nares. Its lateral surface is almost entirely united 

 to the palatine bone and the pterygoid process, but a small part is free in the pterygo- 

 palatine fossa. The hamulus is distinctly hook-like, thin, and sharp. 



The_ nasal bone is little more than half the length of that of the horse. It is 

 straight in its length, but strongly curved from side to side. It does not fuse later- 

 ally with the adjacent bones, even in old age. The posterior extremity is pointed 

 and fits into the notch between the frontal bones. The anterior end is broader, 

 and is_ divided into two parts by a deep notch. In old animals there is a small 

 extension of the frontal sinus into this bone. 



The lacrimal bone is very large. The extensive facial part is concave in its 

 length, and bears no lacrimal tubercle. The orbital margin is marked by several 

 notches. The orbital part bears ventrally the remarkable lacrimal bulla;' this is a 

 large and very thin-walled protuberance, which bulges backward into the lower 

 part of the orbit, and contains an extension of the maxillary sinus. The fossa for 

 the lacrimal sac is small, and is just behind the orbital margin. 



The malar bone is relatively long. The facial surface is extensive ; it bears a 

 curved crest (Crista facialis) just below the orbital margin which is continued on 

 the maxilla, and below this it is concave dorso-ventrally. The zygomatic process 

 divides into two branches; of these, the frontal branch (Processus frontalis) turns 

 upward and backward and joins the supraorbital process of the frontal bone; 

 the temporal branch (Processus temporalis) continues backward, and is over- 

 lapped by the zygomatic process of the temporal bone, completing the zygomatic 

 arch. 



The dorsal turbinate bone is less cribriform and fragile than in the horse, and 

 is widest in its middle, small at either end. It is attached to the turbinate crest 

 of the nasal bone, and curves downward, outward, and then upward to be applied 

 outwardly to the frontal and lacrimal bones. It thus incloses a cavity which com- 

 municates with the middle meatus nasi. (In the macerated skull it opens into the 

 frontal sinus, but this communication is closed by mucous membrane in the fresh 

 state.) 



The ventral turbinate bone is shorter but much broader than in the horse. It 

 is attached to the maxilla by a basal lamella about an inch (ca. 2 to 3 cm.) wide, 

 which slopes ventro-medially. At the inner edge of this it splits into two plates 

 which are rolled in opposite directions, and inclose two separate cavities, sub- 

 divided by several septa. The dorsal one opens into the middle meatus, the 

 ventral one into the ventral meatus nasi. 



The vomer forms a wider and deeper groove than in the horse. Its anterior 

 end rests in a groove formed by the ends of the palatine processes of the premaxillse. 

 The anterior third of its thin ventral edge fits into the nasal crest of the maxilla; 

 behind this it is free and is separated by a considerable interval from the nasal floor. 



The two halves of the mandible do not fuse completely even in advanced age, so 

 that a symphysis mandibulse is present. The symphyseal surfaces are extremely 

 rough and are marked by reciprocal projections and cavities. The body is shorter, 

 wider, and flatter than in the horse, and has eight round and relatively shallow 

 alveoli for the lower incisors. The interalveolar border is long, curved, thin, and 

 sharp. There are no alveoli for the canine teeth, which are absent. The anterior 

 part of the ramus is narrow. The mental foramen is further forward than in the 

 horse, and is in the posterior end of a fossa. The rami diverge more, so that the 

 mandibular space is wider than in the horse. They are also more strongly curved, 

 and the angle is more pronounced. The molar part is not so high, especially in its 

 anterior part. Its ventral border is convex in its lengih. Its alveolar border bears 



