44 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 119 



large specimens with four or five, sharp-toothed ridges, and as many- 

 pointed marginal teeth present on denticle; median tooth on denticle 

 slightly longer than more distal teeth; pedicel very short, moderately 

 slender. 



Individuals deep olive to brownish-gray dorsally, shading to white 

 ventrally; tip of ventral siu"face of pectoral fin faintly gray-black to 

 dark black in life. 



Maximum total length probably between 12 and 13 feet. 



Variation. — With the possible exception of the teeth, Sphyrna 

 lewini shows little noticeable geographic variation in external mor- 

 phological characters. This can be seen from table 5, in which mor- 

 phometric data have been recorded from specimens from throughout 

 the range. Those characters that are considered to be of basic tax- 

 onomic importance, such as the structure of the chondrocranium (pi. 

 6b), the form of the anterior-median pore patch on the underside of 

 the head (fig. 22d), the length and development of the intranarial 

 groove, the position and length of the gill slits, and the shape and 

 position of the fins, remain quite constant. 



Although the teeth in Sphyrna lewini are ordinarily smooth, in 

 some cases they may be very weakly serrate. This apparently occurs 

 only in larger specimens, at least 5 or 6 feet in length. The serrated 

 condition has long been thought to be characteristic only of the 

 Pacific population (Sadowsky, 1965, p. 2), and, in fact, was one of the 

 reasons for Springer's naming the Atlantic popidation as a new species, 

 S. diplana. However, Dr. Shelton P. Applegate has recently informed 

 me (in litt.) that he has seen specimens of this species from the western 

 Atlantic with serrated teeth. In view of this, and because there seem 

 to be no concomitant characters to suggest that more than one species 

 is involved, I choose to regard S. diplana as a synonym of S. lewini. 



A series of nine vertebral counts is available for specimens from 

 widely scattered parts of the range. Although the total number of vertebrae 

 ranges from 174 to 204, variation in eight of the nine individuals is 

 only from 192 to 204. The reduced count in the other specimen 

 (USNM 25180— from Charleston, S.C.) is due both to a decreased 

 number of body and caudal vertebrae. It is diflBcult to say at this 

 time what the significance of this unusually low count is. 



Range — Sphyrna lewini is circumtropical in distribution (map 3). 

 In the western Atlantic it occurs from southern Brazil (and possibly 

 Uruguay) north to New Jersey (Bigelow and Schroeder, 1948, p. 419; 

 Backus, 1960, p. 244). In the eastern Atlantic its range is not so 

 well defined. It occurs in the Mediterranean Sea (Bigelow and Schroe- 

 der, 1948, p. 419) and along the African coast south at least to Liberia 

 and Ghana (Bigelow and Schroeder, 1948, p. 419). The northern 



