Whalebone Whales 



and constitute the largest known animals. The whales and their 

 allies are grouped in several families as follows: 



I. Whalebone whales (Family Balcenidce). Size very large 

 (length 30-85 feet), mouth enormous, no teeth, but the 

 upper jaw provided with long strips of whalebone. 



II. Sperm whales (Family Physeteridce). Teeth all along the 



lower jaw, but absent entirely from the upper. Length 

 1 0-80 feet. 



III. Bottle-nosed whales (Family Ziphiidce}. One tooth on each 



side of the lower jaw or with no visible teeth at all; 

 a narrow projecting snout. Length 20-30 feet. 



IV. Dolphins and porpoises (Family Delphinidce). Teeth nume- 



rous in both jaws (or with one long horizontal tusk in 

 the narwhal). Head in some species rounded in front 

 while others have a projecting snout. Length 5-15 feet. 



WHALEBONE WHALES 



Family Balcenidce 



This family includes all of the true whales or toothless whales, 

 as they are variously called, and the only large "whale" not 

 included here is the sperm whale which is really more closely 

 allied to the porpoises and dolphins. The whales are charac- 

 terized by their immense size, enormous head, and total absence 

 of teeth. Small teeth are, it is true, formed very early in their 

 development, but they are entirely absorbed before birth. 



Another peculiarity of the family is the presence in the mouth 

 of "baleen" or whalebone. This consists of thin, flexible, horny 

 plates, somewhat triangular in outline, which are attached cross- 

 wise down each side of the roof of the mouth. The inner 

 edges of these plates are much split up and frayed so that the 

 slender filaments form a sieve reaching from the top to the bot- 

 tom of the mouth, by which the water is strained away from 

 the small marine animals that are scooped up by the whale and 

 which constitute its food. By raising the tongue in the nearly 

 closed mouth the water is expelled from the lips and the food 

 remains. 



There is a popular idea that the water taken into the mouth 

 is discharged through the nostril or "blow hole" situated on 



