FAMILIES OF PERISSODACTYLA. 



703 



The stomach is simple ; the caecum is large ; there is no 

 gall-bladder. 



The mammae are inguinal ; the placenta is diffuse and 

 non-deciduate. 



Families of Perissodadyla. 



Family TapiridsE. — In the tapirs (Tapirus) there are four digits in 

 the manus, but the third ringer is still practically median, as the 

 fifth digit scarcely reaches the ground. The hind-foot has three 



digits. The dentition of the genus is 3ii|. The orbit and 



temporal fossa are continuous. The nose and upper lip form a 



Fig. 310. — Side view of Horse's skull, roots of teeth exposed. 

 — From Edinburgh Museum of Science and Art. 



P., Parietal ; F. t frontal ; u. , nasal ; pm, % premaxilla ; ?«., maxilla ; 

 j. y jugal ; /., lachrymal; sq., squamosal ; pp., paroccipital pro- 

 cess; c, canine ; C\, condyle. 



short proboscis. The thick skin has but scanty hair. In habit, 

 the tapirs are shy and nocturnal, fond of forests and water, 

 feeding on tender shoots and leaves. The distribution is some- 

 what remarkable, for four species live in Central and South 

 America, while a fifth is Malayan. The genus was once 

 widespread, but has survived in these two far-separated regions. 

 Family Equidas. — In the modern horses {Equus) there is on each 

 foot one functional digit — the third, with splints representing the 

 metacarpals and metatarsals of the second and fourth. Professor 

 Cossar Ewart has recently found in the embryo of the horse the 

 rudiments of the three phalanges of the second and fourth digits. 

 The vestigial phalanges of these digits subsequently fuse with 

 one another and with the respective metacarpals or metatarsals, 

 forming "buttons" at the end of the splints. The ulna and 

 fibula are incomplete, but the former is quite complete in the 



ftetus. The dentition is 2£*3 but the first premolar is rudi- 

 3143 r 



