696 MAMMALIA. 



"33 



Examples: Camelus, , the Arabian camel (C. dromedarius] 



3 T2 3 



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



1123 



has two humps. The genus Auchenia , includes the 



3123 



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

 forms than the camels, and without humps. 



Group 3. Tragulina, comprising the family Tragulidse or Chevrotains. 

 These are small animals, u intermediate in their structure between 

 the Deer, the Camels, and the Pigs." There are four complete 

 toes on each foot, but the second and fifth are slender ; the third 

 and fourth metacarpals and metatarsals are fused in Tragzilus, 

 free in the other genus Dorcatherium ; the fibula is complete. 

 There are no upper incisors, the upper canines are long and 

 pointed especially in the males, the lower canines are like 



OI 33 



incisors, the dental formula is . The Chevrotains ruminate, 



. 3T33 

 and the stomach is divided into three chambers. The placenta 



FIG. 252. Stomach of Sheep. (From LEUNIS.) 



a, (Esophagus ; c, rumen or paunch ; d, reticulum or honeycomb 

 bag ; e, psalterium or many-plies \f, abomasum or reed ; l>, beginning 

 of duodenum. 



is diffuse. The Chevrotains are often confusedly associated with 

 the musk deer (Moschus) with which they have no special affinities. 

 Species of Tragulus (smallest among living Ungulates) occur in Indo- 

 Malaya, India, and Ceylon ; one species of Dorcatherium , of aquatic pig- 

 like habits, is found on the west coast of Africa. 



Group 4. Pecora or Cotylophora the true Ruminants, including deer, 

 giraffes, cattle, and sheep. Only the third and fourth digits are 

 complete, the fused third and fourth metacarpals and metatarsals 

 form " cannon bones." In the embryos of ox and sheep, the 

 second and fifth metacarpals and metatarsals are also represented ; 

 the second metacarpal and fifth metatarsal are unstable and soon 

 disappear ; small traces of the fifth metacarpal and second 

 metatarsal persist. Paired outgrowths of the frontal bones are 

 common, capped with horny sheaths in the Bovidre, deciduous 



