FAMILY DELPIIINID^j; NARWHAL, INIA. 243 



really single ; but the fact is, that the rudiments of two teeth 

 are always present, and this not in the male only, but in the 

 female. Sometimes the tooth on the right side is developed ; 

 sometimes that on the left ; the corresponding tooth remaining 

 small, or even permanently concealed. But instances are occa- 

 sionally met with, in which both teeth have been developed to a 

 considerable extent, even in the female. The use of the tooth 

 seems to be merely that of an organ of defence ; it cannot assist 

 the animal in obtaining its food ; for this consists merely of 

 mollusks and other soft animals. Its body much resembles that of 

 the Beluga in form, and agrees with it in being without a dorsal 

 fin. It is an active powerful creature, swimming with almost 

 Incredible swiftness ; it inhabits the northern seas, rarely 

 coming so far south as even the Orkney Islands. When attacked, 

 it shows great ferocity ; and has been known to drive its horn, 

 or rather tusk, deep into the thick oak timbers of a ship. 

 Besides these, may be mentioned the Inia ; a remarkable fresh- 

 water genus of Delphinidae, inhabiting the remote tributaries of 

 the Amazons, some thousands of miles from the sea. It has the 

 external form of the Dolphin, with some coarse bristly hairs on 

 the snout ; the lips are deeply cleft ; and the nostrils are placed 

 far back, above the paddles. A female specimen measured 

 seven feet in length ; and the males are stated to be double that 

 size. Two or three other species of Dolphins from the fresh 

 waters of South America have lately been described. 



213. Of the family CATODONTID^E, only two species are 

 known ; the common Cachalot, or Spermaceti Whale ; and the 

 high-finned Cachalot. The former is the one which is the object 

 of pursuit, on account of the oil and spermaceti which it yields ; 

 the latter is comparatively rare. The head of the Spermaceti 

 Whale nearly equals the rest of the body in length, and surpasses 

 it in bulk. This enormous size, however, is not due to the great 

 development of the brain ; but to the presence of a very large 

 receptacle for the Spermaceti, which lies in a hollow on the upper 

 part of the cranium. This receptacle consists of a dense bag, 

 divided into compartments ; and the substance which it contains 

 is in a semi-fluid state, consisting of Spermaceti united with oil. 



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