SKELETON OF PERISSODACTYLA. 



449 



301 



Skull of American Tapir. 



sHglitly incurved : they are strengthened by a long post-tympanic 

 process, developed from the squamosal and articulated to the fore 

 part of the base of the paroccipital, so as to circumscribe a space 

 occupied by the true mastoid which is confluent with the petrosal. 

 One or two vacuities are left in this space for the exit of veins. 

 The post-glenoid process is much developed. The base of the 

 l^terygoid process is perforated lengthwise by the ectocarotid ; the 

 apex is slightly recurved, and unites with the palatine by a 

 squamous suture. The en- 

 topterygoids are thin, small, 

 curved lamellaa applied to 

 the inner side of the base 

 of the pterygoid processes, 

 and uniting with each other 

 below, and clear of, the pre- 

 sphenoid. The major part 

 of the palatine enters into 

 the formation of the laro:e 

 oblique hinder aperture of 

 the nasal passages : the smaller anterior division completes the bony 

 palate which terminates behind between the first and second true 

 molar. The lacrymal canal commences by two distinct orifices. 

 The bases of the nasal bones are deeply grooved, and articulate with 

 the frontals parallel with the back part of the orbit. There is no 

 superorbital foramen or canal. The premaxillaries terminate 

 behind at a considerable distance from the elevated nasals. In 

 the American Tapir (Taphnis Americcmus), fig. 301, the super- 

 occipital is narrower and more deeply excavated than in the 

 Malayan Tapir : a smaller proportion of the petromastoid is 

 visible between the exoccipital and squamosal, r/ : the frontals, ii, 

 are less expanded and less elevated above the nasals, is. The 

 petromastoids fit, but not closely, the vacuities on each side the 

 basioccipital. In the cranial cavity the rhinencephalic fossa is 

 well defined. 



In the (Sumatran) Rhinoceros, a smaller proportion of the 

 palatine bones enters into the formation of the bony palate than 

 in the Tapir; they chiefly form the sides of the hinder nasal 

 aperture, the anterior boundary of which is opposite the first true 

 molars. The pterygoid processes are perforated at their base, 

 lengthwise, by the ectocarotid arteries. The nasofrontal suture 

 is in advance of the orbits. The postglenoid process is long, 

 subtrihedal, and obtuse : the })ost-tymi)anic process takes the 

 place of the mastoid and is here a strong quadrate process 



VOL. II. G a 



