THE CAMELS. 157 



Nothing can well be said in opposition to this. 

 Our illustration below (Fig. 22), gives the upper 



FIG. 22. Auchenia hesterna. Second Molar of the Left Upper 

 Jaw. Nat. size (after Leidy). 



molar of one of those Diluvial llamas, the Auchenia 

 hesterna, in the natural size. 



trapezoid. The metatarsals have coalesced and become the 



A n q 



* canon-bone.' Then conies Pliauchenia with : cheek-teeth, 



o 3 



q q A O 



Camelus, ] - , Auchenia - . A more and more con- 

 2 o 1 o 



tinuous delay in the formation of the teeth is observed ; the 

 teeth eventually no longer cut the gum, and finally disappear 

 completely, a process which is repeated in many other lines. 

 The occurrence of the llama in South America shows that the 

 causes which led to its extinction in North America did not 

 exist in the southern continent. 



