CANIDiE. 477 



The normally developed deciduous molars are : — 



. 3-3 1-1 3-3 



m. — : c. — ; m. — : = 28. 



3—3 ' 1—1 ' 3—3 



The predecessors of the iSrst permanent premolars in both jaws 

 are seldom calcified, and generally disappear after being transitorily 

 manifested in the papillary stage ; the second, third, and fourth 

 milk-molars which are developed and in use by the young animal, 

 are those only which are enumerated in the deciduous formula. 

 The incisors appear about the third week after birth, the middle 

 ones first cutting the gum, and the other teeth following in the 

 order of their position ; the last molar is in place before the end 

 of the sixth week. In the Dog, at three months old the succes- 

 sors of the deciduous teeth present the development represented 

 in PL 125, fig. 4. The deciduous incisors (i) and canines (c) differ 

 from their successors chiefly in their smaller size ; the crowns of 

 the canines are more recurved. The first molar {d \) is conical with 

 two widely diverging fangs, in both jaws : the second in the upper 

 jaw {d 2) is the sectorial tooth, and has a relatively shorter blade, 

 and the tubercle is continued more nearly from the middle of the 

 inner side, than in the permanent sectorial : the third upper molar 

 {d 3) resembles the first permanent tubercular molar, but has a 

 less tuberculate inner lobe. In the lower jaw the first deciduous 

 molar resembles that above, but has the anterior and posterior 

 basal tubercles better marked ; the second is similar, but larger ; 

 the third is the sectorial tooth, in which the biconical blade is 

 shorter in proportion to the posterior quadrituberculate broad lobe, 

 than in the permanent sectorial. 



The first permanent premolar {p 1) comes into place before 

 any of the deciduous teeth are shed : its germinal predecessor 

 disappearing before birth. The second upper premolar {p 2) re- 

 sembles in form the first deciduous molar which it displaces. The 

 third upper premolar {p 3) is a more simple tooth than the sectorial 

 molar which it displaces : the upper permanent sectorial {p 4) displaces 

 the deciduous tubercular molar. The tw^o permanent true molars 

 (m I, m 2) succeed each other horizontally without displacing any 

 teeth. In the lower jaw the second and third premolars have 



