THE HOOFED MAMMALS. 135 



although, as in all the pigs, the normal three pairs of these teeth are 

 retained in the lower jaw. The premolars are reduced to three pairs 

 in the upper, and two in the lower jaw; but in aged animals not only- 

 all these teeth, but likewise the first two pairs of molars, are generally 

 shed, so that there is only the last pair of molars left in each jaw behind 

 the tusks. These last molars are of great size and very peculiar structure, 

 being composed of a number of narrow cylindrical columns arising from 

 a common base, and closely packed together, so as to form a long, 

 narrow, tall crown. Different as such a tooth looks at first sight from the 

 corresponding molar of an ordinary pig, a closer inspection will show that 

 it is nothing but a highly specialised modification of the same general 

 type. 



All pigs are more or less nocturnal in their habits, associating in droves, or 

 " sounders," of variable size, and inflicting much damage on crops by their 

 habit of grovelling in the soil in search of roots with their snouts. In diet 

 they may be said to be omnivorous, scarcely anything edible coming amiss to 

 them. The females produce a large number of young at a birth, and thereby 

 differ very remarkably from the ruminants, in which the number very 

 seldom exceeds two, and is more generally one. Boars attack with their 

 lower tusks, and the wounds inflicted by these formidable weapons are 

 terrific, a horse being not unfrequently ripped open by one sweep from the 

 tusk of a charging boar. 



Although nearly allied to the pigs of the Old World, with which they 

 appear to be still more intimately connected by means of certain ex- 

 tinct types, the small American swine known as peccaries 

 (Dicotyles) are generally regarded as indicating a family Peccaries. — 

 group by themselves. They are specially distinguished by Family 



the circumstance th;it the canine teeth of the upper jaw Dicotylidce. 

 have their points directed downwards in the ordinary 

 manner, with their hinder edges sharpened to a cutting edge ; and likewise 

 by the toes on the hind-feet being reduced to three. In the skeleton the 

 third and fourth metacarpal and metatarsal bones are united at their 

 upper ends. Another peculiarity is to be found in the circumstance that the 

 last premolar in the upper jaw is as complex as the first molar, its crown 

 carrying four distinct tubercles. The stomach also is of a more complicated 

 construction than that of the true pigs ; and the back is provided with a 

 peculiar gland, from which these animals derive their scientific title. The 

 total number of teeth is 38, there being only two pairs of incisors in the 

 upper jaw, and three pairs of premolars in each. Peccaries, which range 

 from the Red River of Arkansas to the Rio Negro of Patagonia, much 

 resemble small blackish pigs in general appearance. They are forest-haunting 

 animals ; and although of small size individually, the large droves in which 

 they collect render them foes by no means to be despised by the lonely 

 traveller in the Brazilian or Paraguayan forests. 



The three preceding families of the sub-order Artiodaotyla constitute a 



sectional .group known as the Suina, and are collectively characterised by the 



tuberculate molar teeth and the circumstance that the third 



Camel Tribe. — and fourth metacarpal and metatarsal bones of the feet (that 



Family is to say those corresponding to the third and fourth digits 



Cameiidce. of the human hand and foot) are never completely united 



together, and are iu most cases entirely separate. The rO' 



maining members of the sub-order are divided into three other sections, all 



