THE MAMMALS OF NEW JERSEY. 41 



aa. Size medium or large (lO to 80 feet), large teeth along the lower jaw 

 but absent from the upper. physETERID^ (Sperm Whales.) 



aaa. Size medium (20 to 30 feet), one tooth on each side of the lower jaw, 

 or teeth absent; a narrow projecting snout. 



ziPHiiD^ (Bottle-nosed Whales.) 

 aaaa. Size small (5 to 15 feet), teeth numerous in both jaws, head in some 

 species rounded in front, in others with a projecting snout. 



DELPHiNiD^ (Dolphins and Porpoises.) 



Family BAL^Nip^. 



Whalk-Bone Whales. 



This family comprises all the large whales with the exception 

 of the Sperm Whale, and they are generally known as Tooth- 

 less Whales or Whalebone Whales. In the very early stages 

 of their development small teeth are formed, but these entirely 

 disappear before birth. 



The mouth of these whales is filled with thin, heavy plates 

 of baleen or whalebone attached crosswise down each side of 

 the roof of the mouth. The inner edges are much lacerated 

 forming a sort of seive, sO' that when the tongue is pressed up 

 against the baleen the water in the mouth is forced through and 

 passes out at the lips leaving any small animals or other food 

 stranded on the seive. 



There is a popular idea that water is forced out of the mouth 

 through the nostril or "blow hole," but this is an error; the 

 so-called "spout" of the whale being due merely to the con- 

 densation of moisture in the discharged breath, perhaps com- 

 bined with some water which may be thrown up if the discharge 

 begins while the head is still slightly below the surface. 



Our Whalebone Whales belong to three genera, which may be 

 distinguished as follows : 



a. No fin on the back, throat not furrowed, upper jaw highly arched and 

 narrow. balaena 



aa. Dorsal fin present, throat deeply furrowed longitudinally, upper jaw not 

 arched, skull flat and broad. 

 h. Back humped, flippers very long and scalloped on the edges. 



MEGAPTERA 



hh. Back not humped, flippers moderate, not scalloped. balaenopTera 



