DENTITION. 



and the same in the lower jaw. This is usually expressed shortly 

 by a formula, thus : I.f, C. \, Pm.*, M. = ~, the letters 

 denoting the kind of teeth, the upper numbers the number 

 of each kind on one side in the upper jaw, the lower 

 numbers those in the lower jaw, so that in the example above 

 given there would be eleven teeth on each side in both the 

 upper and lower jaws, or forty-four in all. As has already been 

 mentioned, a greater or less number of these teeth may be 

 wanting in different animals and the formula will differ 

 accordingly: thus in man it is 1. 1, C.}, Pm.jj, M.y = g or 

 thirty-two in all. In the cat it is 1. 1, C. ~, Pm.|, M. \ = * 

 or thirty in all. 



Among living mammals the elephants are perhaps the most 

 remarkable. Not only do they exceed in size all other living 

 land-animals, but they are further distinguished by the possession 

 of a mobile trunk or proboscis, which is at once a sensitive 

 organ of touch and a most efficient means of grasping objects, 

 both large and small. Furthermore, the structure of their teeth 

 reaches a degree of complication not to be found in any other 

 animals. At the same time, though in many respects so peculiar, 

 in others they retain primitive characters that have been lost in 

 most of the other Ungulata, with which they are usually classed. 

 The most notable of these primitive characters is the presence 

 of the original five toes on each foot,' while in most hoofed- 

 animals the feet have become " specialised " by the loss of one 

 or more of the digits. 



It is now proposed to describe some of the principal stages 

 by which the elephants gradually came to be what they are at 

 the present day, and to show that the earliest-known forms 

 were much like other primitive hoofed-animals, a condition 

 to which the pigs and tapirs among living mammals perhaps 

 most nearly approach. It will be shown that the earliest- 

 known animal belonging to the Proboscidea or elephants was, 

 in fact, not unlike a large pig (see fig. 8), though in some 

 respects an even more primitive creature. From this beginning 

 we can trace a gradual increase in size in the later forms, a 

 gradual development of the trunk or proboscis, first as the 



