NO. 3539 HAMMERHEAD SHARKS GILBERT 43 



straight or slightly falcate; apex and inner corner of pectoral fin 

 rounded; pelvic fin equal in length or slightly less (about four-fifths as 

 long) than anal fin; pelvic fin base approximately equal in length to 

 anal fin base; anterior margin of pelvic fin weakly convex, the distal 

 margin nearly straight; anal fin equal in length or slightly greater than 

 pelvic fin; height of anal fin about a third again as much as height of 

 second dorsal fin; caudal fin nearly a thii'd of TL; upper margin of 

 caudal fin nearly straight; terminal part of caudal about one-fifth of 

 total length of fin; posterior margin of terminal part of caudal fin 

 moderately falcate; terminal apex of caudal narrowly rounded; lower 

 lobe of caudal relatively narrow and long, the distance from angle 

 included by upper and lower caudal lobes to tip of latter going from 

 1% to 2 times in anterior margin of lower caudal lobe; lower caudal 

 lobe one-third to two-fifths as long as upper lobe; lower caudal lobe 

 fairly erect, sloping posteriorly at about a 35° angle from a perpen- 

 dicular to body axis; anterior margin of lower caudal lobe weakly 

 convex; posterior margin of lower lobe nearly straight. 



Anterior margin of rostral node of chondrocranium nearly straight, 

 or with a very shallow median indentation; accessory rostral cartilages 

 absent; anterior fontanelle (viewed ventrally) appearing broad and 

 shallowly U-shaped, with no noticeable median notch; prominent, 

 bluntly rounded wings present on sides of rostral node; anterior wing 

 of olfactory cartilage prominent, pointed, and projecting medially; 

 anterior part of preorbital process long and slender, with a sharp angle 

 on anterior edge; posterior part of preorbital process terminating in an 

 evenly rounded knob. 



Total number of vertebrae 174 to 204 (in nine specimens examined; 

 only one individual with less than 192); body vertebrae 86 to 100, the 

 relative number of body to caudal vertebrae varying from six more to 

 twelve less. 



Teeth ; teeth sometimes weakly serrate in 



15 or 16-1 or 2-15 or 16 



large individuals; first tooth smaller than second, the 15th and 16th 

 very small; teeth 1 through 3 in upper jaw nearly symmetrical and 

 erect, with the subsequent teeth becoming increasingly oblique 

 toward corners of mouth; cusps present on all teeth; lower teeth with 

 somewhat narrower cusps than uppers, similarly oblique, but with 

 successive series tending to become more erect and their cusps relative- 

 ly more narrow with growth. 



Dermal denticles (examined from upper part of back beneath first 

 dorsal fin) closely overlapping, the blades thin and moderately arched ; 

 length of denticle (measured to tip of median marginal "tooth") as 

 great, or nearly as great, as width; small specimens usually with thi'ee, 



