46 PROCEEDINGS OF THE NATIONAL MUSEUM vol. no 



uncataloged) , from the same geographic area. Photographs of these 

 appear in plate 10 and radiographs in plate 9. 



The most striking difference between the two heads is the deeper, 

 more robust appearance of S. couardi (also see measurements in table 

 10). This is confusing, since Cadenat described S. couardi as having a 

 "longer and smaller" head than S. lewini; however, this apparent 

 discrepancy may simply be a matter of semantics. The overall 

 appearance of the head, in fact, seems closer to S. mokarran than S. 

 lewini; however, couardi and mokarran may readUy be distinguished 

 by the presence of a distinct intranarial groove and nonserrated teeth 

 in the former species, and by chondrocranial structure and differences 

 in pore patterns on the ventral surface of the head. 



The mucal pore patches on the ventral surface of the head are 

 basicaDy similar in S. couardi and S. lewini, although the anterior- 

 median patch in the former is completely separated medially instead 

 of being divided about halfway as in the latter (fig. 22d). The 

 chondrocrania of the two forms also are similar (pis. 9 a, b), the main 

 difference being in the appearance of the preorbital process. In (S. 

 couardi this structure is shorter and has a distinct knob at the angle, 

 whereas in S. lewini it is longer and lacks a distinct knob. In addition, 

 the olfactory wings in S. couardi are blunt and do not come to a sharp 

 point as in S. lewini. In this case, however, the wing tips are rather 

 ragged in appearance, suggesting that this possibly may be an aberrant 

 condition. 



In conclusion, the above evidence seems to indicate that Sphyrna 

 couardi is a valid species of restricted range and that it is most closely 

 related to Sphyrna lewini. 



Subgenus Platysqualus Swainson 



The subgenus Platysqualus, which is here considered to include 

 Sphyrna tudes, S. media, S. corona, and S. tiburo, is distinguished by 

 the following unique characters: First and fifth gill slits nearly equal 

 in length and both somewhat shorter than the three middle slits ; anal 

 fin and anal fin base longer than in any other group of sphyrnids, the 

 former 11.0 to 13.5 percent, and the latter 7.5 to 9.0 percent, of TL; 

 anal base a fourth to half again as long as pectoral base; upper pre- 

 caudal pit broadly semicircular or slightly pointed in shape, the ends 

 pointing anteriorly (figs. 21e-'i) ; lower precaudai pit present (this 

 featm-e also sometimes present in S. lewini); fifth gill slit above in- 

 sertion of pectoral fin (slightly posterior in S. tiburo); lobe of first 

 dorsal fin extending past insertion of pelvic fin (in all but S. tiburo) ; 

 teeth weak, nonserrated, with narrow pointed cusps; accessory rostral 

 cartilages often present (none observed in S. tiburo). 



