THE PEEISSODACTYLA. 



343 



the head is provided with homy appendages, they are en- 

 tirely epidermal and devoid of a bony core ; and they are 

 placed in the middle line of the skull. 



Fig. 93. 



m'\ 



Fig. 93. — A, Front aspect of the left tarsus of a Horse. 1. Calcaneum. 

 2. Astragalus. 3. Naviculare. 4. Ectocuneiforra. 5. Cuboides. 



B, Posterior aspect of the left metatarsus of a Horse. 1. The me- 

 tatarsal of the third digit. 2, 3. The metatarsals of tlie rudimentary 



digits. 



The Perissodactyla consist of the existing families Equidce, 

 BhinocerotidcB, and Tapiridce, and of the extinetPalceotJieridce 

 and Macrauchenidce. 



a. The Equidce, or Horses and Asses, have one toe on 



