HAMMERHEAD SHARKS — GILBERT 



27 



For many years the species herein called Sphyrna mokarran was 

 known as Sphyrna tudes. Tortonese (1950b, pp. 1030-1033) was the 

 first to point out that the three type specimens of Zygaena tudes 

 actually comprise two species, one of which may be S. mokarran. 

 Only two of the types are apparently now extant (one from Nice, 

 France; the second from Cayenne, French Guiana), neither of which 

 is S. mokarran. However, since the missing specimen is from an 

 area (Coromandel, India) where the species represented by the two 

 existing types does not occur, and since there is a fairly close super- 

 ficial resemblance between the two species in question, one can assume 

 that the Coromandel individual was probably Sphyrna mokarran. 



Figure 6. — Sphyrna mokarran: a, juvenile male, 673 mm. TL, from Englewood, Fla. 

 (USNM 106543); b, head, 0.2 X (USNM 106543); c, dermal denticles, about 49 X 

 (USNM 106543). (From Bigelow and Schroeder, 1948, p. 430.) 



Diagnosis. — Characters mentioned in the diagnosis of the sub- 

 genus Sphyrna are not repeated here. 



Sphyrna mokarran is unique among members of the genus Sphyrna 

 in having a deeply falcate pelvic fin and strongly serrated teeth at all 

 sizes. S. mokarran is also characterized by a deep median indentation 

 (scallop) on anterior margin of head; absence of an inner narial groove, 

 this structure represented by a thin line; a tall second dorsal fin, the 

 height of the fin slightly greater than height of anal fin; a short second 

 dorsal lobe, the length of the lobe equal to height of fin and extending 

 only about one-half of distance from posterior part of fin base to upper 



