17 



HI. EDENTATA (toothless). — b'requently with toothless jaws. Central 

 incisors and canines always wanting. Teeth, when present, are without 

 enamel, rootless, and monophyodont. Premaxillse always small. Well- 

 developed claws adapted for grasping (sloth), digging, or scratching. An 

 ancient order, exhibiting great variety of forms, e.g. Eradypus (sloth — 

 confined to South America); Ant-eater; Armadillo. Distribution — South 

 America, South Asia, South and East Africa. 



IV. UNGULATA (hoofed). — Limbs used only for progression (never 

 for prehension), for which they are adapted by (1) absence of pollex and 

 hallux; (2) metacarpal and metatarsal regions elongated and upright in 

 position; (3) digits are enclosed in hoofs; (4) absence of clavicles. Herbi- 

 vorous in diet; hence alimentary canal is long, and molars have broad flat 

 crowns, the enamel folds of which are characteristic. Placenta indeciduate. 



1. Pbrissodactyla (odd-toed). — Ungulates with an odd number of digits 



in the pes, the middle digit being the most developed. Horns, when 

 present (e.g. rhinoceros), are epidermal structures, and situated 

 medially on the nose, one before the other if two horns. A knob 

 (third trochanter) on the femur. Stomach simple. e.g. Tapir 

 (S. America, Malay, Sumatra, and Borneo), Ehinoceros (Oriental), 

 Horse. 



[OroMppus the oldest fossil horse, found in Eocene strata was about the 

 size of a fox, had four complete digits and a, fifth rudimentary one. 

 Miohippus (in Miocene strata) and Plioliippus (in Pliocene strata) are 

 intermediate forms.] 



2. Artiodactyla (even-toed). — Ungulates with an even number of digits 



in the pes. The two outer digits usually rudimentary, and the two 

 middle ones of equal size, and rest on the ground. Horns, when 

 present, paired (one on each side), and have a bony core — an out- 

 growth from the frontal bone. No third trochanter. Complex 

 stomach. 



{a) Bunodontia (tubercle-toothed). — Non- ruminating Artio- 

 dactyls. Molar teeth, with tuberculate enamel croions or transverse 

 enamel ridges, e.g. Pig, Hippopotamus (Africa), Peccary. 



(b) Selenodontia ( crescentic - toothed ). — Artiodactyls A\hich 

 ruminate. Molar teeth have crescentic enamel ridges on the crowns, 

 and incisors usually upon 3. Upper incisors and canines often 

 absent, e.g. Sheep (ovis). Ox, Goat, Camel, Llama, Giraffe (Africa), 

 Deer (horns in the form of antlers, — solid bone, outgrowth from 

 the frontal bone — which can be shed). 



V. SIEENIA. — Marine mammals, adapted to an aquatic herbivorous 

 (seaweed-eating) life by (1) thick, almost hairless skin; (2) fish-like tail, 

 horizontally flattened; (3) fore-limbs converted into paddles — no hind limbs; 

 (4) dentition incomplete. Molars have flattened crowns. The nostrils are 

 far forwards, not at the top of the head as in whales, v.g. Manatee (original 



