I I 2 VERTEBRATES : MAMMALS. 



The Genus Balcsnoptera comprises Whales with a dor- 

 sal fin and short baleen, and known under the names of 

 Fin-backs, Razor-backs, and Rorquals. They equal and 

 in many cases much exceed the B. mysticctus in length, 

 some have been seen one hundred feet long, but yield 

 far less oil. They are exceedingly powerful and rapid in 

 their movements, and are captured with the greatest dif- 

 ficulty and danger. One or two species are common on 

 the North Atlantic coast of America. 



PHYSETERIDjE, OR SPERM-WHALE FAMILY. This Fam- 

 ily comprises Whales with excessively enlarged heads, 

 and whose upper jaw has neither teeth nor whalebone, 

 and whose lower jaw is narrow, elongated, and corre- 

 sponds to a furrow in the upper one, and is armed on 

 each side with a range of cylindrical or conical teeth, 

 which, when the mouth is closed, fit corresponding cavi- 

 ties in the upper jaw. The upper portion of the head 

 Fig. 8 3 . consists mainly of 



large cavities, sepa- 

 rated and covered by 

 cartilages, and filled 

 with an oil which be- 

 comes fixed as it cools, 

 and is known under 

 the name of sperma- 



Head of Sperm Whale. ^^ J^e body yields 



sperm oil. The substance known under the name of am- 

 bergris is a concretion formed in the intestines of Sperm 

 Whales. These animals inhabit deep, tropical, and tem- 

 perate seas, and never enter the Polar regions. 



The Genus PJiyseter comprises the Sperm Whales 

 proper. 



The Great Sperm Whale or Cachelot, P. macrocephalus, 

 Shaw, is the largest and most important species, equal- 

 ling the Right Whale in size, averaging sixty feet in 



