117 



fore, the only way of obtaining useful information from the mass of 

 figures was to calculate the average indices of the different teeth. The 

 following table shows such indices of the teeth on the right and left 

 sides of the ten mandibles, and also of the two sides taken together. 

 It may be inferred that the figures are reliable from the fact that there 

 is practically no difference between the three columns. 



The average indices of the lower cheek-teeth of the 

 horse, calculated from ten mandibles. 



Remembering that the breadth of the lower cheek-teeth of the 

 horse is approximately the same throughout the series, the above 

 table gives a very fair notion of the length of the various teeth. The 

 higher the index the shorter the tooth. It is evident then that the 

 last is the longest tooth ; this being closely followed by the first (pm^). 

 From the same evidence it is apparent that the shortest teeth are 

 m^ and pm"^: pm^ and m^ occupying an intermediate position. The 

 great length of the first and the last tooth depends largely upon the 

 circumstance that those ends of them which are not in contact with 

 other teeth are narrow and somewhat elongated. 



We have now something definite with which to compare the teeth 

 in the abnormal specimens. Their dimensions (in mm) and indices 



