The Sharks-Part One 293 



A relatively rare shark in U.S. Atlantic coastal waters, the Six-Gilled 

 is abundant enough in the Mediterranean to be considered a nuisance 

 because it drives off more marketable fish. 



It is a deep-water shark, but it has been seen swimming at the surface 

 off the Irish coast. A 26-footer was once reportedly caught off Cornwall, 

 England. Large Six-Gills, weighing as much as 1,600 pounds, have been 

 hauled up from 700 fathoms off Cuba, where they are frequently caught. 

 Normally, the Six-Gilled does not grow to more than 15V^ feet. 



The Six-Gilled is also known as the Cow shark. Gray shark. Mud 

 shark, or Shovel-Nosed shark. 



The experts do not agree on how many species of Seven-Gilled sharks 

 there are. But there is general agreement that there are only two genera— 

 Heptranchias, whose species have narrow heads, and Notary nchus, 

 whose species have broad heads. Because the species attributed to each 

 genus are so similar, some scientists believe that there are only two spe- 

 cies, one for each genus. 



Seven-gilled shark (Notorynchus maculatum) . 



Courtesy, California Bureau of Marine Fisheries 



Using this division, we have the Narrow-Headed Seven-Gill {Hep- 

 tranchias perlo Bonnaterre, 1788) and the Broad-Headed Seven-Gill 

 {Notorynchus Tnaculatum Ay res, 1885). 



H. perlo is found in both the eastern and the western Atlantic and in 

 the Mediterranean. Although relatively rare in U.S. continental waters 

 of the western Atlantic, it is found from Portugal to the Cape of Good 

 Hope in the east. This species, or one very similar to it, is also found 

 off Japan in the north Pacific. The Seven-Gill of AustraHa (where it is 

 called the One-Finned shark) is considered another species {H. dakini) 

 by some scientists. It is said to have startlingly bright emerald-green eyes, 

 and to grow to about 3 feet. H. perlo is believed to grow to 7^2 feet, 

 though 10-footers have been reported. Although comparatively little is 

 known of its habits, it is believed to be a bottom-dweller in coastal 

 waters both deep and shallow. Its name is sometimes Mud because of its 

 dull brown or grayish coloring. It is also known as the Cow shark. 



N. maculatum, known to grow to 10 feet and reputedly to 15 feet. 



