187—6 
SIWALIK AND NARBADA PROBOSCIDIA. 
isthmus of dentine, formed by the abrasion of a mesial longitudinal bridge. We 
liave already seen that a similar condition occurs in the homologous tooth of the 
jaw represented in fig. 3 of Plate XXIX. The valley between the second and 
thii’d transverse ridges is still open, and these two ridges would not be connected by 
an isthmus of dentine until the tooth was much more worn down than at present. 
Second ^ Third true molars . — The two last molars in the Sind jaw are consider- 
ably wider than either of the jDreceding teeth : the penultimate tooth carries two trans- 
verse ridges, and has only a very slight trace of a posterior talon ; in the latter 
respect it differs from the homologous tooth of the jaw represented in fig. 1 of 
Plate XXIX : it also differs from that tooth in having merely a very slight trace 
of a longitudinal bridge, and consequently, although the two teeth are in almost 
exactly the same state of wear, exhibits no worn dentine surface projecting from 
the hinder ridge into the transverse valley. 
Third true molar . — The last or third true molar (right side of figure) , also car- 
ries two transverse ridges, and has a large three-cornered j)osterior talon, and a low 
longitudinal bridge projecting from the second ridge into the transverse valley. In 
all its characters, this tooth agrees precisely with the homologous tooth in the jaw 
represented in fig. 1 of Plate XXIX, and, therefore, needs no further description. 
Dimensions of lower jaws. — In the following table the dimensions of the three 
lower jaws of Dinotheriuni described al)ove are compared together. The dimen- 
sions in the first column of that table {a) are those of the specimen represented in 
Plate XXX ; those in the second column {h) are the dimensions of the specimen 
represented in figs. 2 and 3 of Plate XXIX ; while the dimensions given in the 
third columir (c) are those of the specimen represented in fig. 1 of the latter 
idate. 
^ ’ c 
Length of four last teeth 
Ditto last premolar 
Width of ditto 
Length of first true molar 
Width of ditto 
Length of penultimate true molar . 
Width of ditto ditto 
Length of last true molar 
Width of ditto 
Depth of jaw at penultimate true molar 
'thickness of ditto at ditto 
Ditto of enamel of first true molar 
Ditto ditto second ditto 
9-3 
1-8 
21 
1-74 
205 
2-34 
2-4 
. !■.? 
2T 
2-4 
2-9 
2-15 
2T5 
2-9 
3T8 
2-25 
2-45 
5-4 
3-4 
01 
OT 
OTo 
0-16 
Comparisons . — If we compare the dimensions of the first lower true molar of the 
specimen represented ir fig. 3 of Plate XXIX with the dimensions of the homo- 
logous upper tooth of Dinotheriuni jpentapotamice, figured and described in a previous 
fasciculus of this volume,^ we shall find that the length of the latter tootli is 
' “ Molar Teeth and other Ecmains of Mammalia/’ pp. 56-74, Plate IX, fig. 2. 
