56 



PROCEEDINGS OF THE NATIONAL MUSEUM 



Sphyrna media differs from S. corona in having a narrower postor- 

 bital process to the chondrocranium, with the anterior edge of this 

 structure posterior, rather than anterior, to the angle formed by the 

 juncture of the innerorbital and anterior mediorbital cartilages (pi. 7c) ; 

 a slightly deeper anterior fontanelle; and shorter rostral cartilages. 

 The last difference has been objectively shown by dividing the trans- 

 verse distance between the tips of the preorbital cartilages into the 



Figure 14. — Sphyrna viedia: a, adult male, 900 mm. TL, from Panama Bay (UCLA 58-304); 

 b, head of same specimen, about 0.12 X; c, dermal denticles of same specimen; d, upper 

 and lower teeth, left side, of same specimen, about 1.5 X. (Drawings by Dorothea B, 

 Schultz.) 



length of the rostral cartilage. For S. media the range of values thus 

 obtained is from 18.1 to 24.0 percent, and for S. corona from 25.9 to 

 30.5 percent; these have been plotted and may be seen in figure 17. 



Sphyrna media also differs from S. corona in having a slightly 

 shorter snout. A comparison of snout lengths may be seen in figures 

 156, 16, and 186. Although there is some overlap in values for the 

 two species, when specimens of a comparable size are compared lower 

 values are obtained for S. media. 



