NO. 3539 HAMMERHEAD SHARKS — GILBERT 69 



caudal appearing relatively narrow and long, the distance from the 

 angle included by the upper and lower caudal lobes to tip of latter 

 going about IK times in anterior margin of lower caudal lobe; lower 

 caudal lobe about one-third as long as upper lobe; lower caudal lobe 

 rather erect, sloping posteriorly at about a 25 to 30° angle from a 

 perpendicular to the body axis; anterior margin of lower caudal lobe 

 weakly convex; posterior margin of lower lobe nearly straight. 



Anterior margin of rostral node of chondrocranium with a broad, 

 deep, median indentation; accessory rostral cartilages usually present; 

 rostral fenestra usually absent (present in one individual examined) ; 

 anterior fontanelle (viewed dorsally) deep and broadly V-shaped, with 

 an indistinct median notch on the posterior margin; prominent, 

 broad, obtusely pointed wings present on sides of rostral node; 

 anterior wing of olfactory cartilage prominent, pointed, and projecting 

 medially; tip of preorbital process short (though not as short as in 

 S. mokarran), rather thick, with a sharp angle on the anterior edge; 

 postorbital process terminating in an angular knob, the anterior 

 corner of which may be either broadly pointed or narrowly rounded, 

 and the posterior corner of which forms a broadly rounded angle. 



Total number of vertebrae numbering from 195 to 202 (iBve speci- 

 mens examined); body vertebrae numbering from 107 to 110, there 

 being from 12 to 25 more body than caudal vertebrae. 



^ ,, 15-0-15 J 16-0-16 ,^ . ^ J 1 ^^ 



Teeth ,^ , ,, and (two specunens counted; latter count 



16-1-15 15-1-15 ^ 



for lectotype) ; upper teeth oblique, becoming increasingly so toward 



corners of mouth in upper jaw; teeth 4 or 5 to 11 longest, the outer 



teeth very low, but with a definite cusp; in lower jaw teeth 2 to 7 or 



8 longest, the outermost two very short, rounded, without a definite 



cusp; one or two series of teeth functional in alternating rows along 



sides of lower jaw, and two to three rows along sides of lower jaw. 



Dermal denticles (examined from upper part of back beneath first 

 dorsal fin) evenly and closely spaced, overlapping but little, the blades 

 thick and rather strongly arched; length of denticle (measured to tip 

 of median marginal "tooth") less than width; small specimens with 

 three, larger specimens usually with up to five, sharp-topped ridges, 

 and as many sharp-pointed marginal teeth (especially deep and pointed 

 in small individuals) on denticle; median tooth on denticle slightly 

 longer than more distal teeth; pedicel long and rather slender. 



Individuals gray or grayish brown dorsally, becoming progressively 

 more pale below; no markings on fins. 



Variation. — Examination of the lectotype (designated elsewhere 

 in this paper) of Zygaena tudes, a 346 mm. female from Nice, France, 

 indicates that the Mediterranean and western Atlantic populations of 

 Sphyrna tudes are morphologically indistinguishable. The only un- 



