850 



PHYLUM CHORDATA : CLASS MAMMALIA 



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 stomach shows a complex rumen with glandular " water- 

 cells," a tubular psalterium, and an abomasum. The Camelida^ 

 are unique among Mammals in having oval instead of circular 

 red blood corpuscles. The placenta is diffuse. 



T T O O 



Examples. — Camelus, — —, the Arabian camel (C. dromedarius) 



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

 has two humps. The camel has a very small area of visible 

 perspiration on the back of the neck, and seems to have a 

 somewhat variable body-temperature, two associated facts which 

 may be adapted to conserving the animal's water-supply in arid 



T TO '3 



countries. The genus Auchenia, -, includes the llama, 



3123 



Fig. 504.— Stomach of sheep. — From Leunis. 



a, CEsophagus ; c, rumen or paunch ; d, reticulum or honeycomb- 

 bag ; e, psalterium or many-plies ; /, abomasum or reed ; b, 

 beginning of duodenum. 



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 

 fifth are slender ; the third and fourth metacarpals and meta- 

 tarsals are fused in Tragulus, free in the other genus Dor- 

 catherium ; 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 incisors ; the dental formula is - — -. 



3133 



The Chevrotains ruminate, and the stomach is divided into three 

 chambers, the many-plies being rudimentary. The placenta is 

 diffuse. The Chevrotains are often confusedly associated with 

 the musk-deer {Moschus), with which they have no special 

 affinities. 



