HISTORY OF THE AKTIODACTyLA 363 



identification, tell but little of the structural changes which it 

 is desirable to know. It is merely a question of time, when 

 more adequate material will be obtained. 



1. TagassuidoB. Peccaries 



The peccaries, or American swine, are now chiefly of Neo- 

 tropical distribution, extending into the Sonoran region only 

 as far as Arkansas ; but this has been true only since the Pleis- 

 tocene, for nearly the entire history of the family has been 

 enacted in North America. In many points of structure the 

 peccaries of the present day are more advanced and specialized 

 than the far more varied and diversified true swine of the Old 

 World, for it is a singular fact that such a long-lived and per- 

 sistent stock as the peccaries should have given rise to so few 

 variants and side-branches. Existing peccaries all belong to a 

 single genus (Tagassu) and are relatively small animals, of 

 unmistakably pig-like character and appearance, but far 

 smaller than the Wild Boar {Sus scrofa) of Europe, or the Wart 

 Hog {Phacochaerus cethiopicus) of Africa, to mention only two 

 of the Old World swine. 



One characteristic and thoroughgoing difference between 

 the peccaries and the swine is the shape of the canine tusks. 

 In the former, the tusks, though 

 very effective weapons, are not 

 very large and are straight and 

 have a vertical direction, while in 

 all the true swine the upper tusk is 

 curved upward and outward, pro- ^'°- i9i -Dentition of the Coi- 



lared Peccary (Tagassu tajacu) left 

 jecting strongly from the side of side, i S, external incisor. C, 



the jaw, and the great, curved camne ^ 2, second premolar (the 

 ■■ ' o ; first is lost), mi, first molar. 



lower tusk wears against its an- 

 terior side. The peccaries further have smaller and simpler 

 molars, each with four principal, conical cusps (quadrituber- 

 culate pattern) arranged in two transverse pairs, with 

 numerous very small cuspules around and between them, 



