174 



KEY TO MARINE MAMMALS (Cont.) 



37 Dorsal fin low and thick, located 1/3 the distance from snout to 

 tail; length of dorsal fin two or more times its height; flipper 

 length equal to or greater than one-sixth of body length; teeth rel- 

 atively slender, not more than 1.3 cm in diameter, located in the 

 anterior portion of the jaw (thus the length from the first to last 

 tooth is markedly shorter than the length of the jaw); mouth directed 

 downwards, at an angle of 30-45 to the horizontal body axis; prom- 

 inent hump on anterior edge of flipper. SHORT-FINNED PILOT WHALE 



37' Dorsal fin thin, situated in the middle of the body, or somewhat 

 more towards the head; basal length of fin less than twice its 

 height; flipper length one-seventh or less of total body length; 

 teeth relatively thick, 2.7 cm in diameter; teeth extend along 

 entire jaw; mouth less oblique to body axis; anterior edge of 

 flipper smoothly curved (no prominent hump). FALSE KILLER WHALE 



38 Beak distinct (though may be short), with or without a sharp demar- 

 cation between beak and forehead; teeth cone-shaped, not flattened 



at tip. 39 



38' Beak inconspicuous; teeth not conical, the crowns broadened and 

 flattened laterally, or chisel-shaped, slender, and almost totally 

 buried in gums. 40 



39 The long slender beak smoothly joins forehead; 20-27 teeth in each 

 side of both upper and lower jaws; each tooth has a series of fine 

 vertical grooves on the crown (may be difficult to detect, if worn); 

 the halves of lower jaws joined along one-fourth their length. 



ROUGH-TOOTHED DOLPHIN 



39' Beak separated from the forehead by a transverse groove, teeth are 



without grooves and have smooth crowns. 41 



40 Pointed head and moderately stout body; dorsal fin shaped as a low 

 equal-sided triangle somewhat lower than long at the base (but not 

 less than half as high as long); fore and rear edges of the fin 

 forming equal angles with the back; a large white area extending 

 high into the flanks, sharply delineated from the dusky dorsal and 

 anterior areas; a distinct, humped ridge runs from the flukes up 

 the middle of the back; teeth chisel -shaped, very slender, not 

 exceeding 1 mm in thickness, more or less embedded in gums; 



vertebrae number about 98. DALL'S PORPOISE 



