334 STRUCTURE AND ADAPTATION OF TEETH 



the anterior portion of the zygoma, and forming 

 an extensive ante-orbital fossa — an arrangement 

 which is not found in the beaver. The zygomatic 

 arch is thus extended unusually far forward ; and 

 instead of the upward curve, as observed in the 

 Carnivora, the convexity of the arch is directed 

 downwards. Very distant points of attachment 

 are thereby afforded to the variously-directed 

 jfibres of the unusually broad masseter muscle, 

 and the reciprocating antero-posterior or sliding 

 motion of the jaw is provided for. 



Another peculiarity in the skull of the beaver 

 and hare deserves passing notice. 



Great timidity and quickness of hearing are 

 remarkable characteristics of these animals ; and 

 to admit of the free posterior movement of the 

 condyloid process of the lower jaw, the long, 

 bony '* meatus auditorius " ascends obliquely 

 backwards, like a projecting trumpet, thus enabling 

 the animal to catch the slightest sound, and 

 receive warning of the approach of its numerous 

 enemiSs. 



That the beaver was an inhabitant of the 

 British Islands within the historic period there is 

 no doubt. Giraldus Cambrensis gives a short 

 account of their manners in Wales ; but even in 

 his time (he travelled there in 1188) they were 

 only found on the river Teify. " Two or three 

 waters in that principality," says Pennant, " still 

 bear the name in the Welsh lano^uao^e, of the 



