ix.] PALEONTOLOGY AND EVOLUTION. 193 



as, or rather larger than, the posterior ones ; that the 

 second premolar has an anterior prolongation ; and that 

 the posterior molar of the lower jaw has, as Cuvier 

 pointed out, a posterior lobe of much smaller size and 

 different form, the dentition of Anchitherium departs 

 from the type of the Palceotherium, and approaches 

 that of the Horse. 



Again, the skeleton of Anchitherium is extremely 

 equine. M. Christol goes so far as to say that the 

 description of the bones of the horse, or the ass, current 

 in veterinary works, would fit those of Anchitherium. 

 And, in a general way, this may be true enough ; but 

 there are some most important differences, which, indeed, 

 are justly indicated by the same careful observer. Thus 

 the ulna is complete throughout, and its shaft is not a 

 mere rudiment, fused into one bone with the radius. 

 There are three toes, one large in the middle and one 

 small on each side. The femur is quite like that of a 

 horse, and has the characteristic fossa above the external 

 condyle. In the British Museum there is a most in- 

 structive specimen of the leg-bones, showing that the 

 fibula was represented by the external malleolus and by 

 a flat tongue of bone, which extends up from it on the 

 outer side of the tibia, and is closely ankylosed with the 

 latter bone. 1 The hind toes are three, like those of the 

 fore leg ; and the middle metatarsal bone is much less 

 compressed from side to side than that of the horse. 



In the Hipparion the teeth nearly resemble those of 

 the Horses, though the crowns of the grinders are not 

 so long ; like those of the Horses, they are abundantly 

 coated with cement. The shaft of the ulna is reduced 



1 1 am indebted to M. Gervais for a specimen which indicates that the fibula 

 was complete, at any rate, in some cases ; and for a very interesting ramus of a 

 mandible, which shows that, as in the Palaotheria, the hindermost milk-molar 

 of the lower jaw was devoid of the posterior lobe which exists in the hindermost 

 true molar. 



H O 



