EVEN-TOED UNGULATES. 695 



through the skin, arching backwards As far as the forehead, 

 and sometimes forwards and downwards again, the lower pair 

 with a more or less parallel course ; Phacockatrus^ the wart 

 hog. 

 Dicotylidre : The New World Peccaries (Dicotyles\ with a snout 



like that of pigs, with four toes on the fore feet, and three behind. 



The incisors are rooted, the upper canines are directed down- 



2133 

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



3133 

 there is a caecum. 



Group 2. Tylopoda, comprising the family Camelidae 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 



FIG. 251. Side view of Sheep's skull, with roots of 

 back teeth exposed. (From Edinburgh Museum of Science 

 and Art.) 



f, Frontal ; , nasal ; pm, premaxilla ; m, maxilla ; /, jugal ; sq, 

 squamosal ; /, lachrymal. 



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 are ruminant in habit, and the stomach is divided into 

 three chambers, of which the first two have on their walls 

 remarkable pouches, which can be filled with fluid, and closed 

 by sphincter muscles. The Camelidge are unique among Mam- 

 mals in having oval instead of circular red blood corpuscles. 

 The placenta is diffuse. 



