Fishes of the Western North Atlantic 441 



Color. Deep olive leaden or brownish gray above, paler on sides, shading into pure or 

 grayish white below; fins of same color as back or sides, with tips or margins more or less 

 dusky; pectorals black-tipped in some specimens, but not in others. 



Size. Reports of embryos of 450 to 460 mm. and of free-living specimens of only 

 510 to 590 mm. suggest a length of about 500 mm. at birth. Adults seemingly do not 

 mature at less than 7 to 8 feet, are often taken at 9 to 1 1 feet in length, and occasionally 

 12 to 13 feet. It seems likely that the still larger Hammerheads that are reported from 

 time to time are in reality the Great Hammerhead (ludes). The following weights of 

 Hammerheads of different lengths probably refer to zygaena: 1,651 mm., 57 pounds 

 (26 kilo); 3,610 mm., 836 pounds (380 kilo); and 3,810 mm., 900 pounds (409 kilo).'" 



Developmental Stages. Presumably development is ovoviviparous; at least the pres- 

 ence of a placenta has never been reported. As many as 29 to 37 embryos have been re- 

 ported repeatedly as being found in a single female. 



Habits. This is a strong-swimming shark, often seen at the surface with the tips of its 

 first dorsal and caudal fin exposed. But we have never seen or heard of one jumping clear 

 of the water. They are to be met with indifferently far out at sea, or so close in to the shore 

 that considerable numbers are often taken in beach seines or in pound nets. On the West 

 African coast they (or they and diflana) are common in salt-water lagoons; they are also 

 reported in similar situations {e.g., Indian River) in Florida. There is even one report of a 

 Hammerhead of some sort in tidal fresh water in Maryland." 



The diet of the zy gaena-diflana group consists chiefly of fish. Inshore, in the southern 

 part of their range, they feed largely on sting-rays, which they are often seen chasing and 

 which have been recorded frequently from their stomachs. Sting-ray spines are also found 

 embedded in the jaws of Hammerheads, as are the spines of the gaff-topsail catfish 

 {Felichthys). Often the stomach contents of the larger ones contain parts of other sharks, 

 or entire small ones, including their own kind. Where net fisheries for sharks are carried 

 on in warm waters it is their common habit to devour the sharks that are entangled in 

 the nets. In the northern part of their range, skates are a major item in their diet; a 

 Hammerhead of 1,780 mm. caught off Woods Hole in August 1944 had in its stomach one 

 seven-inch scup {Stenotomus) ; they are also known to prey on herring and bass in waters 

 of North Europe, and on Spanish mackerel {Scomberomorus maculatus) and menhaden 

 (Brevoortia) in North America; no doubt they also feed on any other fishes that may be 

 available locally. Their recorded diet also includes shrimp, crabs, barnacles, and Crustacea 

 generally, as well as squid. 



Relation to Man. The considerable number taken in the shark fisheries of southern 

 Florida and the West Indies are utilized for leather, fish meal and liver oil. They also 

 afford good sport to any angler who chances to hook one, for they bite freely and have 

 been described (we have never taken one on light tackle) as so lively that one has been 

 known to die of exhaustion when hooked. 



36. Schultz, J. Mammal., /p, 1938: 484. 37. Gunter, Amer. Midi. Nat., 28, 1942: 316. 



