UNGULATA. 433 



The dental formula, then, for a typical Ruminant animal is 

 o o o o 3 3 3 3 



The departures from this typical formula occur in the Camelidce, 

 the Moschidce, and in some of the Deer. Most of the Deer con- 

 form in their dentition to the above formula, but a few forms 

 (e. g., the Muntjak) have canine teeth in the upper jaw. These 

 upper canines, however, are mostly confined to the males ; and 

 if they occur in the females, they are of a small size. The 

 dentition of the Camelidce (Camels and Llamas) is still more 

 aberrant ; there being two canine-like upper incisors and upper 

 canines as well. The lower canines also are more pointed and 

 stand more erect than the lower incisors, so that they are easily 

 recognisable. 



The group of the Ruminantia includes the families of the 

 Camelidce (Camels and Llamas), the Moschidce (Musk-deer), the 

 Cervidce (Deer), the Camelopardalidce (Giraffe), and the Cavicor- 

 nia (Oxen, Sheep, Goats, Antelopes). 



a. Camelidce. The Camels and Llamas constitute in many 

 respects an aberrant group of the Ruminantia, especially in 

 their dentition, the peculiarities of which have been spoken of 

 above, and need not be repeated here. In their feet, too, the 

 Camelidce are peculiar. The feet are long and terminate in 

 only two toes, which are covered by imperfect nail-like hoofs, 

 covering no more than the upper surface of each toe. The 

 two hinder supplementary toes, which are mostly present in the 

 Ruminants, are here altogether wanting ; and the soles of the 

 feet are covered by a callous horny integument, by which the 

 two toes of each foot are conjoined, and upon which the ani- 

 mal walks. The head in all the Camelidce is destitute of horns, 

 and the nostrils can be closed at the will of the animal. 



The two living genera of the Camelidce are Camelus, compris- 

 ing the trde Camels, and Auchenia, comprising the Llamas and 

 Alpacas of South America. Both of these genera are repre- 

 sented by fossil forms, the former by two species which occur 

 in the Tertiary deposits of the Siwalik Hills, in India, and the 

 latter by two species which occur in the bone-caves of Brazil, 

 and one of which exceeded the horse in size. 



Besides these existing genera, there are the two extinct genera 

 Merycotherium and Macrauchenia. The first of these is only 

 known by some molar teeth, which have been discovered in 

 the drift of Siberia, and which resemble those of the Camel in 

 form. Macrauchenia is a remarkable extinct genus, which is in 

 many respects intermediate between the Perissodactyle and 

 2 E 



