VERTEBRATA: MAMMALIA. 



703 



lates the number of the toes is even either two or four and the 

 third toe on each foot forms a symmetrical pair with the fourth 

 (fig. 388, C) . The dorso-himbar vertebra are nineteen in num- 

 ber, and there is no third trochanter on the femur. If true horns 

 are present, these are always in pairs, and are supported by bony 

 horn-cores. The ajitlers of the Deer are also paired, but they are 

 not to be regarded as true horns. The stomach is always more or 

 less complex, or is divided into separate compartments, and the c&cum 

 is comparatively small and simple. By Kowalewsky the Artiodac- 

 tyla, recent and extinct, are divided into two great groups or 

 sections, in accordance with the nature of the teeth. These 

 two sections were differentiated at a very early period, and 

 they are known respectively as the Bunodonta and Selenodonta. 

 In the " Bunodont " section are comprised only the Pigs and 

 their allies, and the Hippopotamus, in all of which the molars 

 and praemolars have tuberculated crowns (fig, 398). In the 



8. Grinding-surface of the molar and praemolar teeth of a Peccary (Dicotyles 

 labiatus), showing the bunodont type of dentition. (After Giebel.) 



" Selenodont " section of the Artiodactyla the praemolars and 

 molars (fig. 399) have the grinding- surfaces of their crowns 



Fig. 399. Grinding-surface of the molar and prsemolar teeth of the Giraffe (Camelo- 

 pardalis Giraffa), showing the selenodont type of dentition. 



divided each into two crescentic lobes, the convexities of 

 which are turned inwards in the upper and outwards in the 

 lower teeth. Some fossil forms, which are otherwise allied to 

 the Bunodont Artiodactyles, show teeth of a "selenodont" 

 character, and thus form a transition between these otherwise 

 sharply separated divisions of even-toed Ungulates. 



The section Artiodactyla comprises the Hippopotamus, the 

 Pigs, and the whole group of the Ruminants, including Oxen, 

 Sheep, Goats, Antelopes, Camels, Llamas, Giraffes, Deer, &c. 



