22 THE SHEEP AND ITS COUSINS 



A very important distinction between cattle and 

 sheep is to be found in the structure of the upper 

 molar teeth, that is to say, the last three pairs of 

 teeth of the cheek-series. In cattle these teeth 

 form squared prismatic pillars, with an additional 

 column between the two crescents on the inner side, 

 and a large amount of cement on the outer surface. 

 In sheep, on the other hand, these teeth are 

 narrower and less elevated, with no additional 

 column on the inner side, and a smaller amount 

 of cement on the outer surface. 



In common with the great majority of true 

 ruminants, adult sheep possess 32 functional teeth, 

 which are classed as follows : Incisors §, canines ^, 

 premolars |, molars f = 32. These are preceded 

 by a smaller series of deciduous or milk teeth, 

 which may be formulated as mi. §, mc. \, mm. f = 20. 

 The whole of these twenty deciduous teeth have 

 cut the gums by the time the lamb is three or 

 four weeks old. At the sixth month the first of the 

 permanent molars makes its appearance behind the 

 last milk-molar in both the upper and lower jaws ; 

 and at the end of the second year the second per- 

 manent molar has also come into use in both jaws, 

 so that there are then five pairs of cheek-teeth, 

 namely three deciduous and two permanent molars 

 both above and below. In order to distinguish 

 between this stage of development and older sheep 

 in which the anterior premolar may have been shed 



