336 



PRINCIPLES OF ANIMAL BIOLOGY 



elongation of the second pair of incisors in each jaw to form short tusks; 

 the indication of transverse ridges on the molar teeth (F) ; and the position 

 of the nasal openings some distance back of the tip of the upper jaw, 



Fig. 283. — Evolution of the head and molar teetli of the mastodons and elephants. 

 The shuUs on the right are enclosed in the flesh in the form the latter is supposed to have 

 had. A, A', Elephas, Pleistocene; B, Stegodon, Pliocene; C, C, Mastodon, Pleistocene; 

 D, D', Triloi^hodon, Miocene; E, E', Palaeoinastodoii, Oligocene; F, F' , Moeritherium, 

 Eocene. {Frorn Lull, "Organic Evolution," courtesy of The Macmillan Company.) 



indicating probably a prehensile upper lip. There were 3G teeth, and the 



neck was long enough to enable the animal to put its head to the ground. 



Palaeomastodon, which lived in Egypt and India, dates from early 



Oligocene time. It was of somewhat larger size, the posterior part of 



