366 



MECHANICAL EVOLUTION. 



pendent on that of the masseter muscle, it remains to ascertain a 

 probable cause for the relation of the latter to the dental series in 



modern Carnivora. Why, for 

 instance, were not the last 

 molars modified into sectorial 

 teeth in these animals, as in 

 the extinct Hyanodon, and 

 various Creodo7ita? The an- 

 swer obviously is to be found 

 in the development of the pre- 

 hensile character of the canine 

 teeth. It is probable that the 

 gape of the mouth in the Hyse- 

 nodons was very wide, since the 

 masseter was situated relative- 

 ly far posteriorly. In such an 

 animal the anterior parts of 

 the jaws with the canines had 

 little prehensile power, as their form and anterior direction also 

 indicates. They doubtless snapped rather than lacerated their 

 enemies. The same habit is seen in the existing dogs, whose long 



F G. G7. — Procelurus julieni Filh., two 

 thirds natural size. From the Phosphorites 

 of France. From Filhol. 



^J»5Sf^lSS« V.^l^-SSVWV. 



Fig. 68. — Dinietis cyclops, one half natural size. From John Day Miocene of 

 Oregon. Mus. Cope. From vol. iii, U. S. Geol. Surv. Terrs. 



jaws do not permit the lacerating power of the canines of the 

 FelidcB, though more effective in this respect than those of the 

 HycBnodons. The usefulness of a lever of the third kind depends 

 on the approximation of the power to the weight ; that is, in the 



