18 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 119 



orbit to outer margin of narial opening (at least in smaller specimens); 



teeth relatively weak, median ones often more or less needle-like in 



appearance; lower precaudal pit present (may also be present in S. 



lewini) ; posterior lobe of first dorsal fin extending beyond insertion of 



pelvic fin (in S. tudes, S. corona, and S. media only) ; maximum size 



smaller, the largest specimens probably not over 4 or 5 feet TL ... 3 



3a. Head not widely expanded, greatest width about 21 percent of total 



body length (usually less than 20 percent) ; anterior margin of head 



evenly rounded or slightly pointed in median line, never with 



median notch; posterior lobe of first dorsal fin terminating anterior to 



insertion of pelvic fin; origin of first dorsal fin situated well posterior 



to axil of pectoral fin; eyes not situated distinctly anterior to mouth, 



line drawn between posterior margins of orbits either intersecting or 



passing just anterior to symphysis of lower jaw; upper precaudal pit 



as in figure 21e; anterior-median pores on ventral surface of head as 



in figure 22e; chondrocranium as in plates 7a, b 4 



4a. Head with more evenly rounded anterior margin (fig. 126) ; greatest 

 width of head measuring slightly less as shown in table 6; fig 13 



Sphyrna tiburo tiburo (Linnaeus) 

 Western Atlantic, from New England to southern Brazil. 

 4b. Head with less evenly rounded anterior margin (fig. 12a), usually 

 coming to a point at tip of rostrum; greatest width of head measuring 

 slightly more as shown in table 6; fig. 13. 



Sphyrna tiburo vespertina Springer 

 Eastern Pacific, from southern California to Equador. 

 3b. Head widely expanded, the least width 22 percent of total body length; 

 anterior margin of head not always evenly rounded, usually with a 

 more or less distinct median notch (sometimes evenly rounded in aS. 

 media) ; posterior lobe of first dorsal fin terminating posterior to 

 insertion of pelvic fin; origin of first dorsal fin situated above or slightly 

 posterior to axil of pectoral fin; eyes situated anterior to mouth, line 

 drawn between posterior margins of orbits passing well anterior to 

 symphysis of lower jaw; upper precaudal pit not as in figure 21e; 

 anterior-median pores on ventral surface of head not as in figure 22e; 



chondrocranium not as in plates 7a, b 5 



5a. Inner narial groove present; well-defined median notch present on 

 anterior margin of head; anterior-median pores on ventral surface 

 of head as in figure 22h; chondrocranium as in plates 8a, b. 



Sphyrna tudes (Valenciennes) 



Gulf of Mexico south to Uruguay; also recorded from western 



Mediterranean Sea. 



5b. Inner narial groove absent; no well-defined median notch present on 



anterior margin of head (poorly defined notch may be present in 



some individuals) ; anterior-median pores on ventral surface of head 



not as in figure 22/i; chondrocranium not as in plates 8a, b . . . 6 



6a. Distance from tip of snout to symphysis of upper jaw slightly shorter, 



usually less than 40 percent of head width (table 7; fig. 16); anal 



fin more deeply falcate, with a more pointed apex (figs. 14a, 15a) ; 



mouth slightly broader (figs. 146, 156) ; anterior-median pores on 



ventral surface of head as in figure 22/; chondrocranium as in 



plate 7c; maximum size possibly larger, the largest specimen 



