58 Field Museum of Natural History — Zoology, Vol. XI. 



Family CASTORID^. Beavers. 



Tail broad and flat (paddle shaped) , hairless and covered with scales ; 

 hind feet broadly webbed; skull stout; incisors noticeably large and 

 strong. The general character of the skull is sciurine, but postorbital 

 processes are absent and the infraorbital foramen is nearly concealed 

 by a large nearly vertical ridge of the maxilla; the auditory meatus is 



Skull of a Beaver. (About ;?-3 nat. size.> 



long and tubular and extends upward above level of the zygoma; 

 lower leg bones separate; five toes on both fore and hind feet; second 

 toe of hind foot with double or divided claw. 



The family consists of but one genus, Castor, represented in North 

 America by one species and five geographical races. They are large, 

 aquatic Rodents, the largest living representatives of the order in North 

 America, often weighing 40 or 50 pounds, and are much hunted and 

 trapped for their skins, which are one of the best known commercial 

 furs. The anal glands of the Beaver contain a strong scented, oily 

 fluid known as "Castoreum," which is much used by trappers as a bait 

 to attract the animal. It is also used more or less in the manufacture 

 of perfumes, and is claimed to possess medicinal properties. 



The only other living representative of this family is the European 

 Beaver (C. fiber), which is very similar to our species; it differs in being 

 somewhat smaller, the skull is comparatively lighter, and the nasal 

 bones are longer. 



