Order CETACEA. ' Whales and Porpoises 



Mammals greatly modified for an aquatic habitat ; external 

 form fish-like ; body more or less rounded and tapering without 

 distinct constriction in neck region ; tail developed into paired 

 lateral propelling organs or "flukes" which form a horizontal 

 mass of tissue terminating in a notch in the midline; head 

 large; lips immobile; forelimbs modified into swimming 

 paddles with no differentiation into arm, forearm, or digits, 

 and enclosed in a continuous integument ; no external trace of 

 hind limbs; skin usually hairless, smooth, shining; just under 

 skin a thick mass of fatty areolar tissue, the "blubber"; 

 median dorsal fin usually present; nostrils opening through 

 paired or single valve-like aperture near crown of head; eyes 

 small; no external ear, the meatus opening into a minute 

 orifice in the skin. 



Whales and Porpoises will be so seldom seen by most of the 

 users of this field book, at least under circumstances which 

 permit the observation of identifying characteristics, that it is 

 inadvisable to go into details as to specific characterization. 

 For the sake of completeness, however, all of the forms liable 

 to be encountered on our shores are given at least a passing 

 mention, and most of the more common "Whales and Porpoises 

 are described and figured. 



After all, there are great gaps in our knowledge of the 

 Cetacea. The very fact that these animals live in a medium 

 which man can only skirt on the surface, and spend such a 

 great part of their existence under the surface of the water, 

 precludes the intimacy of contact which we may hope to 

 enjoy with the land mammals. We know that many species 

 are great wanderers and that their ranges cover an enormous 

 area. Many are confined by the more or less invisible and 

 unknown barriers of food supply, ocean temperatures, depths 

 and currents, and we have each ocean or sea with its own 

 peculiar cetaceans. There is a great scarcity of recorded 



^ See Miller, Smithsonian Miscl. Coll., Vol. 76, No. S, 1923, for a 



classification of the subgeneric groups of this order. 



557 



