399—18 
SIWALIK AND NARBADA PROBOSCIDIA. 
the antepenultimate, penultimate, and last milk molars, respectively^ The three last 
teeth in the same series, as being developed behind and after the milk-molars, must 
consequently correspond to the true molars of the Pig ; and are, therefore, called 
respectively the first, second and third true molars. 
Now we come to the consideration of the dents des r emplacement or premolars, 
the succession of which requires a little more discussion. In a memoir on elephant 
and Mastodon, by Dr. Palconer,^ puhhshed in part in 1816, the writer seems to have 
been of opinion that apparently in all Mastodons only the penultimate milk-molar 
was succeeded by a premolar [dent de r emplacement'). This conclusion seems to 
have been previously arrived at by Professor Owen, who retains it up to the late 
date of 1861.® Dr. Palconer, however, in a subsequent paper, ‘‘ announced that 
in many species, at least, two premolars were developed, which I infer, though 
this is not clearly expressed, replace the second and third milk-molars. That the 
last upper milk-molar was succeeded by a ‘ dent de r emplacement' is proved by the 
specimens drawn in figs. 6 and 8 of Plate XXXVII of this memoir, as well as by 
many other foreign specimens, from which we arrive at the conclusion that the 
two last milk molars were respectively rejDlaced by vertically succeeding premolars 
in the upper jaw : other specimens (especially a fine lower jaw of M. angustidens) 
show that the two last lower milk-molars were similarly replaced. 
Although it is frequently difficult, as will be noticed in the sequel, to refer 
detached milk-molars and premolars to their proper serial position, there is never any 
difficulty when the teeth occur in the jaw. When all the teeth in a Mastodon jaw belong 
to the milk and true molar series, any one tooth is more worn than the tooth imme- 
diately behind it : when premolars are present, on the other hand, the last premolar 
is less worn than the tooth immediately behind it, whether such tooth be a milk- 
molar or the first true molar. 
Besides the penultimate and last milk-molars, there is good evidence that in 
one species of Mastodon, at least, an antepenultimate premolar was also developed. 
In a young upper jaw of the American trilophodont M. productus, figured and de- 
scribed by Professor Cope,® in front of two three-ridged teeth, which from their 
isomerous ridge-formula, must be the first and second “intermediate” molars, or 
respectively the last milk-molar and the first true molar, there are developed two small 
teeth, which are less worn than the third milk-molar, and which consequently are 
true “ dents des r emplacement," or respectively the antepenultimate and penultimate 
’ For the sake of brevity in the text, I have usually termed these teeth, respectively, the first, second and third milk, 
molars, though, of course, they really correspond to the second, third and fourth of the milk-molars of the typical series. 
According to Falconer the pre-antepenultimate milk-molar is occasionally developed as an abnormality in the African 
elephant. 
^ loc, cit., p. 95. 
® “Odontography,” p. 615, ed. 1840.45. “Palaeontology,” p. 388, ed. 1861. 
* loc. cit., Vol. II, p. II (published in 1857). 
* “ Extinct Vertebrata of New Mexico.” U. S. Geographical Survey, W. of 100th merid., Vol. IV, Pt. II, p. 309, 
PI. LXXI, fig. I. 
