374 SYSTEMATIC ZOOLOGY 



are readily divisible into two suborders according to the pres- 

 ence or absence of teeth. We may note a few, of the common 

 and more interesting species, considering first those which have 

 teeth ; in these there is always a single external nasal opening. 



Of the smaller toothed whales the most common are the 

 following : the two-toothed whales living in the waters about 

 Australia and New Zealand, which are from four to six meters 

 in length ; the white whale, named from its yellowish white 

 color, which lives in the northern Atlantic and Pacific waters 

 and grows to be about five meters long ; the narwhal, which in 

 the male has one of the teeth in the upper jaw excessively long, 

 and projecting forward, forming a tusk from two and a half to 



FIG. 366. Orca gladiator, the killer. (After True, from Parker and Haswell's Manual.) 



three meters long, while the body of the animal is only from 

 four to four and a half meters in length — it inhabits the Arctic 

 seas; and finally the killers (Fig. 366), belonging to the genus 

 Orca, which have a maximum length of from four and a half to 

 six meters and are found in both the Atlantic and the Pacific. 

 The last are extremely destructive animals, killing more than they 

 can eat, feeding on young seals, young porpoises, fishes, and 

 even attacking and killing some of the largest whales, which 

 they overpower by their numbers. 



To the toothed Cetacea belong also the porpoises and dol- 

 phins ; these two popular terms are used interchangeably, but 

 the true porpoises have a rounded head, while the true dolphins 



