MANATEES AND DUGONGS. 263 



enormous specimens of this and allied species are some- 

 times so thrown on our coasts. 



The substances obtained from the whale are, first, the 

 oil which is obtained by melting the fat or blubber, and 

 a single whale may yield eight or ten tons ; then the 

 whalebone, which is used for many purposes. 



The arctic right whale is forty-five or fifty feet long, 

 as is also the humpback, so called from the shape of the 

 dorsal fin. The name balaenoptera is given to the razor- 

 backs, fin-backs, and rorquals, which latter are the largest 

 species. The balsenoptera have folds in the skin of the 

 throat, and very distinct dorsal fins. 



SIRENIA. 



This order contains but two living families, the mana- 

 tees, or sea-cows, and the dugongs. They are found in 



DUGONG (Halicore dugong). 



warm Southern seas and estuaries ; they are inoffensive, 

 gregarious, and herbivorous. Like the cetacea, they 

 have no hind limbs, but the phalanges of the fore limbs 

 are perfect in sirenia, and there are rudimentary nails. 



