KEY TO THE PRINCIPAL EISHES 191 



k. The teeth are slender and awl-shaped 

 with smooth edges 



Porbeagles and Mako Sharks (p. 12). 

 kk. The teeth are triangular, flat, and 

 with fine saw-Hke edges 

 Great White Shark or Man-Eater (p. 14). 

 jj. The external gill-openings are very 

 large, and extend nearly right round 

 the "neck"; the teeth are very 

 numerous, small and conical in shape 



Basking Shark (p. 20). 

 gg. The upper lobe of the caudal fin is more than 

 one-half of the total length of the shark 



Thresher or Fox Shark (p. 24). 

 ff. Grooves are present connecting the mouth with 

 the nostrils ; the last 2 to 4 gill-openings are 

 placed above the base of the pectoral fin. 



I. The caudal fin is long and very asym- 



metrical ; the external gill-openings are 

 of moderate size ; there are no gill-rakers. 

 m. The spiracles are small ; the anal fin is 

 quite free from the caudal fin 



Nurse Sharks (p. 28). 

 mm. The spiracles are large or of moderate size ; 

 the anal fin is either joined to the caudal 

 fin or ends directly in front of it. 

 n. The body is thick-set, with the head 

 and trunk broad and depressed ; the 

 sides of the head are provided with 

 tassels of skin ; the eyes have folds 

 below them ; there are no ridges 

 along the body 

 Wobbegongs or Carpet Sharks (p. 33). 

 nn. The body is long, and the head and 

 trunk are not very broad or depressed; 

 there are no tassels of skin on the 

 sides of the head ; the eyes have no 

 folds below them ; there are keels or 

 ridges along the back and sides 



Zebra Shark (p. 34). 



II. The caudal fin appears nearly symmetrical ; 



the external gill-openings are large ; gill- 

 rakers are present Whale Shark (p. 29). 

 ee. The eye has a third eyelid or nictitating mem- 

 brane ; there are no grooves connecting the 

 mouth with the nostrils ; the last 1 or 2 gill- 

 openings are placed above the base of the 

 pectoral tin. 



