ZOOLOGICAL POSITION AND STRUCTURE 19 
which has only three chambers, owing to the absence 
of the manyplies. The lateral pair of metacarpal 
and metatarsal bones (second and fifth) are, more- 
over, complete, as in the pig (see figure on page 12), 
although of a more slender type, which is never 
the case among typical ruminants ; and in the case 
of one of the two living genera, as represented by 
the African water-chevrotain, the two middle meta- 
carpals do not coalesce into a cannon-bone, but 
remain separate throughout life. There are several 
other features by which the skeletons, and likewise 
the teeth, of chevrotains differ from typical ruminants, 
but the characters mentioned are amply sufficient to 
distinguish the group, which is technically known as 
the Tragulina, from the latter. 
A second sectional group of ruminating mammals 
is represented by the camels of the Old World and 
the llamas of South America, which have two-toed 
cushion-like feet, with broad nails instead of hoofs, 
and are hence collectively called Tylopoda. From 
typical ruminants these animals are further dis- 
tinguished by the presence in the young state of 
three pairs of incisor, or front, teeth, of which 
the outer pair normally persists throughout life ; and 
likewise by the absence of a distinct manyplies, or 
psalterium, to the stomach, which is thus three- 
chambered, as in chevrotains. Again, although in 
the fore-foot the two remaining metacarpals, corre- 
sponding to the third and fourth of the typical series 
of five, as shown in the illustration on page 12, are 
fused into a cannon-bone, as are likewise the corre- 
sponding metatarsals in the hind-limb, yet the 
cannon-bones thus formed differ from those of the 
ox and other typical ruminants by the marked 
