86 
ORIGINAL ARTICLES. 
61 of vertebra). These laminae, or bands, in JE. Sumatranus , are wider 
“ (or if one may so say, broader in the direction of the long axis of 
“ the teeth) than in JE. Indicus. In making the comparison, one 
“ may remark that the distinction is less evident in younger indi- 
“ vidnals, and that there are met with, in all species of Elephants 
“ within certain definite limits, remarkable individual differences in 
“ respect of the width of these laminae.” (Nat. Hist. Bev. ii. p. 75.) 
Here it will be observed, the distinction is propounded subject to 
so many qualifications, as to render it elusive for any practical use. 
I have ascertained, after the examination of a very large quantity of 
materials in India and Europe, that the ridge-formula in the Indian 
Elephant runs thus :— 
Milk Molars. True Molars. 
4, 8, 12 12, 16, 20-24. 
4, 8, 12 : 12, 16, 20-24. 
The increase in the number of the ridges of the successive teeth, 
takes place as in E. primigenius, by increments of 4, repeated in two 
series, the first of which terminates with the last milk molar. The 
second series commences with the antepenultimate or first true molar, 
which constantly repeats the number presented by the last milk 
molar, i. e. 12 ; the penultimate (m. 2) shows an increment of 4, the 
number of its ridges being normally 16. The last true molar never 
shows less than 20, commonly about 22, but sometimes, in the lower 
jaw, attaining as many as 27 ridges. This liability to variation in 
the last true molar is well known, and runs more or less through all 
the species of Elephant and Mastodon * But the ciphers, shown 
above, are very constant, in the three intermediate molars, (i. e. the 
milk molar, and the antepenultimate and penultimate true molars) 
namely, 12 : 12, 16. I do not mean to affirm, that they are absolute 
and invariable ; but that the above formula is a fair exponent of the 
results yielded by a great majority of instances, on the comparison of 
a very large quantity of materials. Eor example, the penultimate 
milk molar (m. m. 8), occasionally presents only 7 ridges; while the 
antepenultimate true molar, of the lower jaw, in some cases, exhibits 
as many as 14 ; the variation being dependent, partly on the greater 
or less development of the talon ridges, which are very inconstant, 
and, as I have elsewhere stated, partly on the race, sex, and size of 
the individual.f I rest the more stress upon the importance of the 
ridge-formula, since, whenever the the element of quantity can be 
shown to hold, in the animal organization, it becomes a powerful aid 
* For illustrations of the fact in Mastodon 0Motions, vide Warren. Op. citat. 
p. 79 ; and for its general occurrence in the family, vide Lartet. Bullet. Geol. Soc. 
de France, 2e serie, tom. xvi., note, p. 498. 
f Quart. Jour. Geol. Soc., 1857. Vol. xiii. p, 315. 
