496 
PROFESSOR OWEN ON THE DENTITION OF PHACOCHIERUS, 
crease of size that the antepenultimate grinder is recognizable as the first of the true 
molar series, and the antecedent smaller grinders as the homologues of the milk- 
molars of other Diphyodonts, which milk-molars have no vertical successors in the 
Elephants. In certain Mastodons, however, which are the earliest known forms of 
the Proboscidian family, the last milk-molar was displaced by a vertical successor or 
premolar. Two incisors, moreover, were developed in the lower jaw of the young 
Mastodons, one of which was retained in the male of the Mastodon giganteusoi North 
America, and both in that of the Mastodon longirostris of Europe. 
The human dentition deviates from the typical formula by the suppressed develop- 
ment of several teeth ; as might be anticipated from the characteristic shortness of 
the jaws, which is such as only to allow space for the comparatively few teeth re- 
tained, in close juxtaposition, without any break in the series. 
The numerical formula is 
. 2-2 
* 2 - 2 ’ 
1-1 2-2 
^ 1 - 1 ’ -^ 2 - 2 ’ 
ra|^=32; 
the principal phases in the development of this dentition may be symbolized as 
follows : — 
TO ij -2-2 1-1 2-2 
I. 3 years old, * 2 ^’ ^ 
all of the deciduous series, the molars answering to d 3 and d4 of the typical denti- 
tion. 
TT -2-2 1-1 3-3 
II. 7 years old, t c ^^^ = 24; 
the molars being d3, dA, m 1. 
2 2 1 1 3 3 
III. lOto 12years old, ^ ”*3^“^“^’ 
the molars being p3,p4, ml, and the milk incisors and canines replaced by the per- 
manent ones. 
2 2 1 1 4 — 4 
IV. 12 to 16 years old, i ^ c — j, m — ~^ = 2S, viz. p3,p4, m 1, m 2. 
2 2 1 1 5 5 
V. 18 to 30 years old, i - — c — j, m - — —=32, viz. p3,p4, ml, m2, m 3. 
The teeth which are wanting in Man to complete the typical formula are iS, pi 
and j 9 2. The teeth in Man which answer to the carnassials of the Lion and other 
Ferae are jo4 in the upper jaw, or the second bicuspis of human anatomy, and m I in 
the lower jaw, or the first multicuspid molar. The tooth which is homologous to 
the great complex molar of the Wart-Hog is m3 in both jaws. 
The symbols here proposed to denote the kinds of teeth are, it is hoped, so plain 
and simple as to present no obstacle to the ready comprehension of the facts which 
have been recorded by means of them. Had those facts been explained by means of 
the usual phrases or definitions of the teeth, e. g. “ the second deciduous molar repre- 
