42 MICROSCOPIC ANATOMY OF THE TEETH 



representing the cutting or sectorial type, the talon the 

 crushing or masticating type. 



( Protocone. 

 fTrigon (upper) J Paracone. 



Primitive Triangle . J 1 Metacone. 



I Protoconid. 



j^Trigonid (lower) -I Paraconid. 

 (Metaconid. 



r Talon (upper) Hypocone. 



Heel Hypoconid. 



^Talonid (lower) 



Metaconid. 

 Hypoconulid. 



Talon and The talonid is more developed in the lower molars forming 



Talonid. **.** , , , 



three ot tne nve cusps, the talon only possessing one, the 

 hypocone. In the trigonid of the lower molars the paraconid 

 is suppressed. 



It has been shown, however, by several embryologists 

 that the paracone is the first to appear in the upper molars, 

 although the order of the appearance of the cusps of the 

 lower molars corresponds to the Cope-Osborn theory. The 

 Multi- other principal criticism brought against this theory is that 

 lar Theory, niulti tubercular molars are found in association with tri- 

 tubercular forms in the same geological strata, and it is 

 considered quite as probable that the cusps of higher forms 

 are produced by the suppression of cusps, and not by 

 addition to a single cone. This is ca led the Polybuny 

 or Multitubercular theory. The theory of Concrescence, 

 supported by Ameghino (1), Rose, and Kiikenthal (13), 

 supposes the cusps of human molars to have arisen by the 

 union or concrescence of simple cones. 



According to Bolk, the multicuspidate teeth of the 

 primates have arisen from the fusion of ancestral reptilian 

 teeth, both antero -posteriorly and laterally, the antero- 

 posterior fusion being of teeth of the same series, the lateral 

 fusion, of teeth of separate series. In each case a triconodont 

 tooth has arisen, and these becoming laterally fused, form 

 the six-cusped molar, which he considers the typical mam- 

 malian molar tooth, further modification arising by the 

 addition or suppression of cusps. 



