HAMMERHEAD SHARKS — GILBERT 



67 



third of pectoral fin; base of first dorsal fin three-eighths to four-ninths 

 length of head and from a third again to not quite twice length of 

 pectoral fin base; anterior margin of first dorsal fin broadly and evenly 

 curved, particularly in larger mdividuals, with the part nearest the 

 apex a little more strongly curved ; upper distal margin of first dorsal 

 broadly convex, lower margin broadly but distinctly falcate; lobe of 

 first dorsal fin a little less than one-half length of first dorsal base; 

 origin of second dorsal fin situated about two-fifths of way back 

 above base of anal fin; second dorsal fin tail, its greatest height from 

 two-thirds to four-fifths length of base and from two-thirds to four- 



FiGURE 20. — Sphyrna tudes: a, juvenile female, 402 mm. TL, from Mississippi (USNM 

 195957); h, head of same specimen, about 0.3 X; c, head of small adult, from Gulf of 

 Venezuela (USNM 123217), about 0.18 X. (Drawings by Dorothea B. Schultz.) 



fifths of greatest height of anal fin; second dorsal fin base slightly 

 greater than one-half of anal fin base; lobe of second dorsal fin long, 

 its length from a third to half again greatest height of fin, and ex- 

 tending from two-thirds to three-fourths of distance from posterior 

 part of second dorsal base to upper precaudal pit; pectoral fin from 

 one-half to two-thirds length of head (higher values usually apply to 

 larger individuals); pectoral fin two-thirds as broad as long; length of 

 pectoral fin base from two-thirds to three-fourths length of anal fin 

 base; inner two-thirds of anterior margin of pectoral fin straight, 

 outer third distinctly convex; distal margin of pectoral fin nearly 

 straight or very slightly falcate; apex of pectoral broadly pointed; 



