ELEPHAS (STEGODON). 



35 



M 1 ?=1 M 2 v M 3 =, means that in the first true molar (M 1) 

 there are in the upper jaw 6-7 ridges, while in this case the 

 number in the lower is not known. In the second molar (M 2) 

 there are 6 in the upper, the lower being uncertain, while in 

 the last molar (M 3) there are 7-8 ridges in both the upper and 

 lower jaw. It will be seen, therefore, that the numerator of the 

 fractions represents the number of ridges in the upper teeth,, 

 the denominator the number in the lower. When the two 

 numbers are given thus, 6-8, it means that the number of 

 ridges varies between them. This formula will be employed 

 below in describing the molars, and a table showing the gradual 

 increase in the number of ridges will be given at the end. 



In E. clifti premolars are still developed, but must have 

 been pushed out almost as soon as the milk-molars they replace. 

 The crowns of the molars are quite low, and there is only a 

 small quantity of cement in the valleys between the ridges. 



In Elephas (Stegodori) bombifrons and E. insignis (fig. 22), 

 which represent the next stage, the transverse ridges are some- 

 what more numerous and at the same time are higher, and the 



Fig. 22. 



Vertical longitudinal section of molar tooth of Elephas (Steyodori) insigms. 

 From Lower Pliocene, Siwalik Hills, India. Showing the wide valleys 

 between the cross-ridges filled with cement (), the dark band marked 

 b being the enamel, and beneath that the dentine (c). nat. size. 



valleys are filled with cement to a greater degree. Nevertheless 

 these differences are not very marked, and in the case of indi- 

 vidual teeth it is often difficult to be sure to which of these 



D2 



Pier- 

 cases 

 35, 36. 



Table- 

 case 24. 

 Stand J. 



