170 



KEY TO MARINE MAMMALS (Cont. 



25 



25' 



Mouth situated entirely on extreme lower side of head, upper part of 

 head extending well past tip of lower jaw; lower jaw much narrower 

 than upper; convexity of the blowhole directed sideways and not 

 straight to the rear, OR blowhole S-shaped. 26 



Mouth situated at the fore-end of the snout; lower jaw extending as 

 far or almost as far as front of the head, almost as wide as the 

 snout; convexity of the blowhole directed straight to the rear. 



28 



26 Head very large, up to one-third the animal's total length, squarish 

 in front, and sides very flat in the anterior part; blowhole S-shaped, 

 located at the left front corner of the head; dorsal fin low, shaped 

 as a hump or series of humps on the posterior half of the body; no 

 teeth in upper jaw, tooth sockets present which act as receptacles 

 for teeth of lower jaw when mouth closed. SPERM WHALE 



26' Head about one-fifth the animal's total length, evenly rounded in 

 front; blowhole horseshoe-shaped, situated on top of head, slightly 

 displaced to the left and approximately even with the eyes; dorsal 

 fin slender. 27 



27 No creases on throat; dorsal fin small, located well behind 



midpoint of total body length; 12-16 teeth (rarely 10-11 J in each 



side of lower jaw. PYGMY SPERM WHALE 



27' Inconspicuous creases on throat; dorsal fin tall and slender, located 

 nearer the middle of the back (the anterior portion of the fin is 

 near the midpoint of the body); 8-11 (rarely 13) sharp teeth in each 

 side of lower jaw, rarely 1-3 teeth in each side of upper jaw. 



DWARF SPERM WHALE 



28 Conspicuous grooves on outer surface of throat, converging anteriorly 

 median notch in rear edge of tail flukes absent or inconspicuous; 

 teeth very few and only in lower jaw, sometimes not visible. 



(BEAKED WHALES) 29 



28' No conspicuous grooves on throat; deep median notch on rear margin 

 of flukes; teeth usually numerous in upper and lower jaws, but in 

 exceptional cases upper teeth are absent (Risso's Dolphin) or number 

 only one or two (Narwhal). 31 



