14 Prof. Owen on the Class Mammaiia. 
teeth. In a young Hog of ten months, the first premolar, p. 1, | 
and the first molar, m. ‘L, are in place and use together with the — 
three deciduous molars, hi ts¢. By and d. 4; the second molar, 7 
m. 2, has just begun to cut the gum ; ps 
gether with m, 8, are more or less Cpekatiebe and will be found 
concealed in their closed alveoli.* 
The last deciduous molar, d. 4, has the same relative oe 
ority of size to d. 3 and d. 2, which m. 8 bears to m. 2 and m. a 
and the crowns of p. 3 and p. 4 are of a more simple form ‘al | 
those of the milk-teeth, which they are destined to succeed. 
When the milk-teeth are shed, and the permanent ones are all in 
place, their kinds are indicated, in the genus Sus, by the wee 
ing formula :— 
3-3 4—4 3-3 
ity Oi pep m. yaad: 
which signifies that there are on each side of both upper on 
lower jaws 3 incisors, 1 canine, 4 premolars, and 3 molars, 
making in all 44 teeth, Ba tooth being distinguished by x 
rs age symbol, e. g., p. 1 to p. 4, m. 1 to m. 3. This n 
bes = teeth is never surpassed in the placental Diph yoriont : 
When the premolars and the molars are below this typical 
number, the absent teeth are missing from the fore part 0: the — 
premolar series, and from the back part of the molar series. The — 
most constant teeth are the fourth remolar and the first true 
molar; and these being known by bes order and mode of de- 
velopment, the homologies of the remaining molars and premo- _ 
re are determined by ¢ counting the molars from before backwards, 
‘one,’ ‘two,’ ‘three, ; ans the premolars fron behind forwartiig 
four, ‘three,’ § two,’ ‘on e incisors are counted from the 
median line, commonly the foremost part, of both upper and 
low wer jaws, outwards and backwards. The first ineisor of the = 
duniber and kinds of teeth e.g. “the yn oo and third inci- 
sors,—the first, second, third, and fourth premolars,—the first, 
second, and third molars; and of one side of both jaws in any 
case. 
* T recommend this easily acquired ‘subject? to the young zoologists for 
onstration of the r macraciive li arities 0 f the’ ma corsation, dentition. 
will sett - the premolars must ite 
: molars have no such relations, 
