MAMMALIA 



465 



three main divisions: those of the even-toed forms or 

 Artiodadyla, comprising the pigs, cattle, antelopes, deer, 



Fig. 341. — A side view of a sheep's skull, with the roots of the back 

 teeth exposed. — From Thomson. 



f. t Frontal ; «., nasal ; #m., premaxilla ; »i. t maxilla ; /., jugal ; sq., squamosal ; 

 /., lachrymal. 



and camels ; the odd-toed forms or Perissodactyla, com- 

 prising horses, rhinoceroses, and tapirs : and the elephants 

 or Proboscidea. 



Fig. 342. — The stomach of a sheep.— From Leunis. 



«., CEsophagus ; c, rumen or paunch ; d., reticulum< or honeycomb-bag ; 

 e., psalterium or manyplies ;/"., abomasum or reed; 6., beginning 

 of duodenum. 



The Artiodactyla are distinguished by the fact that the third and fourth 

 digits of each foot are equally developed, and the line which halves the 

 foot runs between them. Thus they have cloven hoofs. The premolars 

 and molars are usually different. The stomach is often complex and 



