42 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 119 



to pit; a slightly less deeply falcate anal fin, the deepest part of the 

 notch on the distal margin situated slightly anterior to a Ime drawn 

 perpendicularly from the posterior axil of the fin; a longer anal base, 

 the length of which is about equal to length of pectoral base; a more 

 obtusely pointed posterior ridge to the upper precaudal pit (fig. 2ld); 

 occasional presence of a lower precaudal pit; presence of a rostral 

 fenestra; and several chondrocranial characters (pi. 6b). 



A comparison of Sphyrna lewini with other members of the genus is 

 presented in table 1. 



Description. — Meristic data appear in table 5. Characters men- 

 tioned in the diagnoses of the subgenus Sphyrna and of aS. lewini are 

 not repeated here. 



Head moderately expanded, the greatest width from 24.0 to 30.2 

 percent of TL (in specimens less than 1,000 mm. long); shallow 

 scallops present on anterior margin of head, about halfway between 

 nares and tip of snout; outer posterior corner of lateral expansion of 

 head posterior to corner of mouth, probably in specunens of all sizes; 

 narial flap broad, moderately pointed at tip, with the outer edge 

 curving evenly inward; orbit large, the horizontal diameter almost 

 equal to length of shortest (fifth) gill slit; length of snout about 

 one-thu'd of head width in smaller specimens, to about one-fifth of 

 head width in larger specimens; greatest transverse distance between 

 corners of mouth from one-fifth to one-fourth of greatest width of 

 head; symphysis of jaws situated posterior to a transverse line drawn 

 between posterior margins of orbits in specimens of all sizes; labial 

 furrow present at corner of lower jaw only (concealed when mouth is 

 closed), about one-fifth to one-fourth as long as greatest horizontal 

 diameter of eye. 



Origin of first dorsal fin above or slightly posterior to axU of pectoral 

 fin, a perpendicidar line drawn ventrally from origin intersecting 

 anterior thu'd of pectoral fin; first dorsal fin broad, rather erect (not 

 as erect as in large specimens of Sj^hyrna tudes), a line drawn perpen- 

 dicularly from apex of fin passing close behind base ; base of first dorsal 

 fin about one-half length of head and from half again to almost twice 

 length of pectoral fin base; anterior margin of finest dorsal fin evenly 

 curved, with part nearest apex very strongly curved; distal margin of 

 first dorsal fin strongly falcate ; lobe of first dorsal fin about one-third 

 length of base ; origin of second dorsal fin situated about halfway back 

 above base of anal fin; second dorsal fin base from three-fifths to four- 

 fifths length of anal fin base; anterior margin of pectoral fin from 

 one-half to two-thirds length of head (higher values usually apply to 

 larger individuals) and about equal to greatest vertical height of first 

 dorsal fin; pectoral fin about two-thirds as broad as long; anterior 

 margin of pectoral fin moderately convex; distal margin of pectoral 



