RUMINANTS. 533 



(fig. 2, e e) they present a secondary fold or indentation at each 

 end. The small internal accessory column is present in this 

 species, but placed deeper in the substance of the tooth than 

 usual, forming a circular island of enamel (p) when the crown 

 is worn a short way down. 



In the Ox (fig. 3) the outer contour of each lobe of the 

 upper molars (o) is more sinuous than in the Antelope or Sheep, 

 the middle convexity being more prominent and the lateral 

 depressions deeper ; the crescentic islands {e e) are not so wide 

 as in the larger Antelopes (fig. 2), and the secondary terminal 

 indentations are less marked at the fore-part of the island. The 

 small internal accessory column (p) forms part of the periphery 

 of the grinding surface at the inner interspace of the lobes, when 

 the crown has been worn down about half an inch, from which 

 part it decreases in size to the beginning of the fangs. 



The upper molars of the Aurochs {Urus, fig. 4) are thicker 

 in proportion to their breadth(l) and have a squarer grinding 

 surface than in the Ox {Bos proper) ; the crescentic islands (e) 

 are simple, with prolonged horns : the internal accessory column 

 (p) is less developed, and is soon indicated by a slight bend of 

 the enamel at the inner interspace of the lobes. 



In the Deer (Cervus) the inner crescentic sub-division {id, fig. 5) 

 of each lobe is thicker transversely than in the Bovidm: in the 

 great extinct Irish Deer {Megaceros, fig. 5) which has molar teeth 

 as large as those of the Aurochs, the crescentic islands are simple, 

 narrow, and more curved or bowed than in the Ox, and in 

 consequence of the later division of the vertical fold of the 

 capsule, the cemental cavity of each is continued into the other 

 until a later period of the attrition of the crown, as shown in the 

 upper molar of fig. 5. 



In the Elk (Subgenus Alces, fig. 6) the central crescents are 

 continuous for a still longer period, and the median transverse 

 fold retaining its full breadth for a greater extent, the crown of 

 the molar continues to be divided, during a longer period of 

 attrition, by a crucial incision ; the crescentic fold — ultimately 



(.1) Breadth is antero -posterior diameter, thickness is transverse diameter. 



