xiy. 



THE ORIGIN OF THE SPECIALIZED TEETH OF THE 



CARJSTIVORA. 



The specially developed teeth of the Carnivora are the canines 

 and sectorials. The former are large in many orders of Mam- 

 malia, and their origin is probably to be sought among the Thero- 

 morphous reptilia,* as Clepsydrops and Deuterosaxirus, if not in 

 still lower types. The successive modifications of form which 

 have resulted in the existing sj)ecialized single lower sectorial 

 tooth of the FelidcB have been already pointed out.f They were 

 shown to consist in the gradual obliteration of the internal and 

 posterior tubercles, and the enlargement of the external anterior 

 tubercle in connection with an additional anterior tubercle. The 

 modification in the character of the dentition, taken as a whole, 

 was shown to consist in the reduction in the number of teeth, un- 

 til in Felis, etc., we have almost the entire function of the molar 

 series confined to a single large sectorial in each jaw. 



Observation on the movements of the jaws of Carnivora shows 

 that they produce a shearing motion of the inferior on the su- 

 perior teeth. This is quite distinct from the sub-horizontal 

 movement of Ruminants, or the vertical motion of hogs and 

 monkeys. Examination of the crowns of the sectorials shows 

 that the inner side of the superior, and the external side of the 

 inferior, are worn in the process of mastication. The attempt to 

 cut the tough and stringy substances found in animal bodies is 

 best accomplished by the shearing of the outer edge of the lower 

 molar on the inner edge of the external tubercles of the superior 

 molar, in an animal with simple tubercular teeth. The width of 

 the mandible is too great to allow the inferior teeth to shear on 

 the inner edge of the inner tubercles of the superior series. The 



* " American Naturalist," 1878, p. 829. 



f Cope, "Proceedings Academy Philada.," 1875, p. 22. 



