TEETH. 



905 



the larger and more lamariform canines of the 

 PaUcotherium (" Odontography," pi. 135., 

 fig. 4.). Tlie CfuBropotamus*, the Anthraco- 

 therium\, the Hyopotamus^., the Hyracothe- 

 rinm, the Oplotherium, the Merycopotamus, 

 the Hippohyus, and other ancient (eocene 

 and miocene) tertiary mammalian genera 

 presented the forty-four teeth, in number and 

 kind according to that which is here pro- 

 pounded as the typical or normal dentition 

 of the placental Mammalia. Amongst the 

 existing genera, the hog (Sits) is one of the 

 few that retain this type. Fig. 578. shows 

 the entire permanent series, exposed, in both 



molar, m. 2, has just begun to cut the gum ; 

 p. 2, p. 3, and p. 4-, together with m. 3, are 

 more or less incomplete and concealed in 

 their closed alveoli. 



The premolars must displace deciduous 

 molars in order to rise into place ; the molars 

 have no such relations ; it will be observed, 

 that the last deciduous molar, d. 4, has the 

 same relative superiority of size to d. 3 and 

 d. 2 which m. 3 bears to m. 2 and m. 1 ; 

 and the crowns of p. 3 and p. 4 are of a 

 more simple form than those of the milk- 

 teeth which they are destined to succeed. 



Teeth of each of the kinds above deter- 



Fig. 578. 



Dentition of the Hog (Sus). 



jaws, and indicated individually by their mined, and arbitrarily named " incisors," " ca- 

 symbols. Fig. 579. illustrates the phenomena nines," " premolars," " molars," have received 

 of development which distinguish the pre- other special names in regard to certain pe- 



Fig. 579. 

 d/, d 3 j. 2 



d\ 



Deciduous and permanent teeth (Sus). Lower jaw. 



molars from the molars. The first premolar, 

 p. 1, and the first molar, in. 1, are in place 

 and use, together with the three deciduous 

 molars, d. 2, d. 3, and d. 4 ; the second 



* History of British Fossil Mammalia, p. 41 G, 

 fig. 164. 



t Jobert, Annales des Sciences, t. xvii. p. 139. 



j Quarterly Journal of the Geological Society, 

 May, 1848, p! 103, pi. viii. 



Geological Transactions. 2nd series, vol. vi. 

 p. 203. 



culiarities of form or other property ; and the 

 ablest comparative anatomists have been led 

 astray in determining their homologies when 

 they have suffered themselves to be guided 

 exclusively by morphological characters. The 

 premolars in the human subject have been 

 called " bicuspids." The last upper pre- 

 molar and the first lower true molar in the 

 Carnivora are termed, from their peculiar 

 form, " sectorials," or " carnassial teeth," 

 " molaires carnassieres " of Cuvier, Teeth 



