424 



CHAPTERS ON THE NATURAL HISTORY 



ward into the mouth, sometimes causing the death of the animal. 

 The molars or grinders may be rootless or the reverse, but are 



Fig. 113. Vertical, Longitudinal Section Through the 

 Skull of a Beaver (Castor fiber). 



Showing the central cavity, the greatly developed turbinal laminas, the mode of implanation of the 

 large, ever-growing, chisel-edged incisor, and the curved, rootless molars. Drawn by the Author after 

 Flower. 



Fig. 114. Side View of the Skull of a Beaver (Castor fiber 



Lower jaw removed, showing teeth in the natural skull. Drawn by the Author after Huxley. 



Fig. 115. Side View of the Skull of a Muskrat (Fiber 



zibethicus). 



never numerous. Their positions are well-shown in my figure of 

 the skulls of the Muskrat and Beaver, here given. In addition to 



