ORIGIN OF THE ELEPHANT'S TRUNK 147 



than the others. It is this (seen in Fig. 20) which has 

 grown larger and larger in later descendants of this 

 primitive form and become the elephant's tusk, whilst all 

 the others have disappeared. 



We now know the complete series of steps connecting 

 elephants with ordinary trunkless, tuskless mammals. 

 The transition from the " beast of Meris " on the one 

 hand to the common typidentate mammalian ancestor, 

 and on the other hand to the elephants, is easy, and 



FIG. 20. Head of the early ancestor of elephants Meritherium 

 as it appeared in life. Observe the absence of a trunk and the 

 enlarged front tooth in the upper jaw, which is converted in later 

 members of the elephant-stock or line of descent into the great 

 tusk. (After a drawing by Prof. Osborne.) 



requires no effort of the imagination. His short muzzle 

 (upper and lower jaw), first elongated step by step to 

 a considerable length, giving us Palaeomastodon (Fig. I 8). 

 Then the lower jaw shrunk and became shorter than it 

 was at the start, and the rest of the muzzle (the front part 

 of the upper jaw, carrying with it the nostrils), drooped 

 and became the mobile muscular elephant's trunk ! 



