S8o MAMMALS. 



Sub-Order Perissodactyla. 

 Horses, Tapirs, Rhinoceros, and their extinct Allies. 



The middle or third digit of fore- and hind-feet is larger 

 than the others, and symmetrical on itself. It may be the 

 only complete digit, as in the horse, or it may be accom- 

 panied by a second and a fourth, and in the fore-foot of 

 Tapirs and some extinct forms, by a fifth digit. No modern 

 forms have any trace of a first digit. The astragalus 

 has a pulley-like surface above for articulation with the 

 tibia; its distal surface is flattened and unites to a much 

 greater extent with the navicular than with the cuboid. 

 The last-named bone is of less importance than in the 

 Artiodactyla. The calcaneum does not articulate with the 

 lower or distal extremity of the fibula. The femur has a 

 a third trochanter or process for the insertion of muscles. 

 There are usually twenty-three dorso-lumbar vertebrae. 



As to the dentition, the premolars and molars form a 

 continuous series, with broad transversely ridged crowns, 

 the last premolars often very like the molars. 



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

 gall-bladder. 



The mamm» are inguinal ; the placenta is diffuse and 

 non-deciduate. 



Families of Perissodactyla. 



Family Tapirids. In the Tapirs ( Tafirus), there are four digits in 

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

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

 digits. The dentition of the genus is |^. The orbit and 

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

 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 some species live in Central and South 

 America, while the rest are Malayan. The genus was once 

 widespread, it has survived in these two widely separated 

 regions. 



Family Equidse. In the modern horses {Equus), there is on each 

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



