XIX. ] 



UNGUI.ATA. 



3.5' 



Various gradational stages between the complete tridac- 

 tyle foot of the Rhinoceros and the monodactyle foot of 

 the Horse are met with in extinct species of the Perisso- 

 dactyla. 



In the Artiodactyla the third and fourth digits are nearly 

 equally developed, and their ungual phalanges are flattened 

 on their contiguous sides, so that together they constitute a 



Kl<;. 116.- Dorsal surface of right laru 

 of khinocero> (A'A/rtiHvnM Sumatra/ 



FH;. 127. Dorsal surface of right tarstifc 

 of Horse (Equus cakaJliiS), \. 



symmetrical form. The second and fifth toes, when present 

 are also equal, but smaller than the others. A line drawn 

 through the centre of the foot has on its tibial side the third 

 digit and metatarsal, the external cuneiform, the navicular 

 and half the astragalus ; and on its fibular side the fourth 

 digit and metatarsal, the cuboid and the other half of the 



