TOOTH- (J'ENESIS IK THE CANID^. 4G3 



regularity " {Darwin) ; while examples of numerical reduction 

 are comparatively common. 



(ii.) Embryology has brought to light the presence o£ vestigial 

 remains of additional teeth. Such examples have been furnished 

 by Oldfield Thomas (26) and M. F. Woodward (30) among Mar- 

 supials, and I have already given reasons for believing that the 

 same are probably present in the Dog. 



One has only to look at such a table as that accompanyiug 

 Oldfield Thomas's (26) paper to see how very general is such a 

 isuppression. 



(iii.) Palseontological evidence shows that a large number of 

 Me.^ozoic Mammals had a greater number of teeth than the 

 ir.ajority of those living. That the tendency to the suppression 

 of teeth has been in ojDeration in past ages is amply testified 

 by Osborn (14) in his paper " On the Structure and Classi- 

 fication of the Mesozoic Mammalia." In this paper he gives the 

 dental formula of the primitive heterodont Mammalia as i. 4, c. 1, 

 pm. 4, m. 8 (p. 249) ; and he goes on to say, " Eeduction of this 

 formula was effected by the loss of the lateral incisors, resulting 

 possibly from the hypertrophy of the adjoining canine ; the pre- 

 molars were reduced by regular antero-posterior suppression, or 

 by the loss of the first or second member of the series ; the 

 molars were reduced either by antero-posterior or by postero- 

 anterior reduction or by simultaneous reduction of both ends of 

 the series." 



And (iv.) if the Mammalia are descended from Reptilian an- 

 cestors, as is generally believed, then certainly a reduction in the 

 number of teeth, as well as in the number of dentitions, muse 

 have taken place. 



Prom these reasons it is possible to conclude, other things being 

 equal, that the member of a mammalian group which has the 

 greatest number of teeth retains, in that particular, the more 

 primitive condition. If this be so, then I think we must regard 

 the UrsidiB among the Arctoidea, the Viverrincs (with the ex- 

 ception of Frio7iodon) among the ^Eluroidea, and Otocyon not 

 only among the Cynuidea, but among the whole Carnivora, as 

 retaining the mo.st primitive condition as to the number of their 

 teeth, which iu the last-named genus is 46 and in one specimen 

 48. That Otocyon is in this respect the most primitive, among 

 the Cynoidea, was a view long ago held by Huxley (7). 



