XIII 



PHYLUM CHORDATA 



543 



the Ruminant Artiodactyles (Fig. 1162) the metacarpals or meta- 

 tarsals of these digits unite to form a single elongated bone, the 

 cannon bone. 



The pelvis of most Ungulata is greatly elongated. The ilia are 

 wide transversely, the syniphysis is very long, involving a part of 

 the ischia as well as the pubes. In the Perissodactyla, but not in 

 the Artiodactyla, there is a well-marked third trochanter. 



In some Ungulates (Rhinoceroses, Tapirs, Pigs, Hippopotami), the 

 fibula is distinct, though slender. In the Horse it is represented 



FIG. 1103. Dorsal surface of 

 right tarsus of Horse (Equus 

 caballus). . astragalus ; c. cal- 

 caneum ; cb. cuboid ; c' 2 . united 

 nicso- and ento-cuneiform ; c3. 

 ecto-cimeiform ; n. navicular ; 

 a. scaphoid ; mil, IV, vestigial 

 second and fourth metatarsals; 

 ///, third metatarsal. (After 

 Flower.) 



FIG. 1164. Dorsal surface 

 of right tarsus of Red 

 Deer (Cervus elaphus). 

 a. astragalus ; c. cal- 

 caneum ; cb. cuboid ; c 3 . 

 conjoined ecto- and 

 meso-cuneiform ; mill, 

 mir, third and fourth 

 metatarsals ; n. navi- 

 cular. (After Flower.) 



FIG. 1165. Dorsal surface 

 of right tarsus of Pig 

 (Sus scrofa). a. astra- 

 galus ; c. calcaueum ; 

 cb. cuboid ; c s , ecto- 

 cuneiform ; c 2 . meso- 

 cuneiform ; mil V. 

 metatarsals ; n. navi- 

 cular. (After Flower.) 



by a vestige. In the Ruminants it is represented only by a small 

 vestige, the malleolar lone, which articulates with the distal end 

 of the tibia. 



The structure of the foot exhibits a close parallelism to that of 

 the manus. The tarsal bones are closely dove-tailed together, 

 and articulate with one another by flat surfaces. The hallux is 

 never developed. In the Perissodactyla the third digit is sym- 

 metrical in itself. In the Rhinoceros and Tapirs the second and 

 fourth digits are also completely developed ; but in the Horses 

 (Fig. 1163) they are represented only by splint-like vestiges of 

 their metatarsals, the metatarsal of the third digit forming an 



L L 2 



