CHAPTER XI. 



THE SKULL IN THE UNGULA.TA, HYRACOIDEA AND 

 PROBOSCIDEA. 



Order Ungulata. Sub-order Perissodactyla. — In the 

 Horse the whole skull is greatly elongated, chiefly in con- 

 sequence of the immense size of the face as compared with 

 the hinder or true cranial portion. The basal line of the 

 skull from the lower border of the foramen magnum to the 

 incisor border of the palate is very nearly straight. The 

 occipital and ethmoid planes are nearly perpendicular to 

 this line, the latter inclining slightly forwards. The ten- 

 torial plane, strongly marked by inward projecting ridges of 

 bone, slopes obliquely backwards at an angle of 45°. The 

 cerebral fossa is a smooth and regular oval, broad and 

 rounded in front, and with no distinct division into 

 anterior and posterior portions. The olfactory fossa is 

 short, but deep from above downwards. The pituitary fossa 

 is very shallow, and there are no distinct clinoid processes. 

 The alisphenoid is very obliquely perforated by the foramen 

 rotundum, but the foramen ovale is confluent with the large 

 foramen lacerum medium behind. There are considerable 

 frontal and sphenoidal air sinuses, but the former do not 

 extend any great distance over the brain-cavity. 



In front of the cerebral cavity, the great tubular nasal 

 cavities are provided with well-developed turbinal bones. 



