ARTIODACTYLA. 



733 



wards, the dental formula is \\ The stomach is complex, and 



3 Z 33 



there is a ccecum. 



Group 2. Tylopoda, comprising the family Camelidie the camels 

 of the Old World and the llamas of S. America. The limbs 

 are long, with only the third and fourth digits developed ; the 

 two metacarpals and metatarsals are united for the greater part 

 of their length, but there is a deep distal cleft ; the tips of the 

 digits have very incomplete hoofs, and the animals walk on a 

 broad pad of skin surrounding the middle phalanges. The 

 femur is long and vertical, and the knee is low down. Of the 

 three upper incisors only one persists in adult life, as an isolated 

 sharp tooth, those of the lower jaw are long and slope forwards. 

 There are canines both above and below. The molars are 

 selenodont. The animals ruminate, and the stomach is divided 



FIG. 359. Side view of sheep's skull, with roots of back 

 teeth exposed. From Edinburgh Museum of 

 Science and Art. 



., Frontal; ;/., nasal ;/;//., premaxilla ; m., maxilla;/, jugal ; 

 sy., squainosal ; /., lachrymal. 



into a rumen with several parts, a tubular psalterium, and an 

 abomasum. The division between the two last is vague exter- 

 nally. On portions of the rumen there are peculiar glandular 

 honeycomb-like cavities, or " water-cells. >: The Camelidce are 

 unique among Mammals in having oval instead of circular red 

 blood corpuscles. The placenta is diffuse. 



Examples. Cainehts. the Arabian camel (C. dfonu'dariiis} 



3123 

 has a dorsal hump of fat, the Bactrian camel (C. bactrianus] 



has two humps. The genus Anchenia, 





includes the 



llama, alpaca, huanaco, and vicugna of S. America, smaller 



forms than the camels, and without humps. 



Group 3. Tragulina or Chevrotains, small animals, "intermediate 

 in their structure between the deer, the camels, and the pigs/' 

 There are four complete toes on each foot, but the second and 



