xm 



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 hone. 



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

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

 the isehia as well as the pubes. In the Perissodaclyla, 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 



Tiijzr 



Fig. 1163.— Doi-sal surface of 

 right tarsus of Horse {Equus 

 caballus). a. astragalus ; c. cal- 

 caneum ; c6. cuboid ; c'-*. united 

 meso- and ento-cuneiform ; c3. 

 ecto-cuneiforni ; n. navicular ; 

 i. scaphoid ; m//, / V, vestigial 

 second and fourth metatarsals ; 

 ///, third metatarsal. (After 

 Flower.) 



Fig. 11154. — Dorsal surface 

 uf right tarsus of Red 

 Deer (Cermts elapkus). 

 a. astragalus ; c. cal- 

 eaneum ; ch. cuboid ; c^. 

 conjoined ' ecto- and 

 meso-cuneiform ; mill, 

 mlV, third and fourth 

 metatarsals ; n. navi- 

 cular. (After Flower.) 



Fig. 1163.— Dorsal surface 

 of right tarsus of Pig 

 (5us scrofa). a. astra- 

 galus ; c. calcaueuiu ; 

 cb. cuboid ; c^, ecto- 

 euneiform ; c-. meso- 

 cuneifoi-ni ; mil— V. 

 metatarsals ; n. navi- 

 cular. (After Flower.) 



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

 vestige, the malleolar hone, 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 ia 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 



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