32 BULLETIN OF THE BUREAU OF FISHERIES 



this specimen contained parts of a man in its stomach is chiefly responsible for the 

 bad reputation of the hammerhead. 



Habits. — The hammerhead is pelagic in habit, often swimming with dorsal and 

 caudal fins above the surface. It feeds chief!}' on fish and squids but is also known 

 to eat crabs and even barnacles. It is viviparous. Thirty-seven embryos have 

 been taken from the oviducts of a female 11 feet long, and probably such specimens 

 as wander north of the Chesapeake Capes give birth to their young in summer, for 

 specimens as small as 13^ feet long have been taken at Woods Hole in July and 

 August. 



THE THRESHER SHARKS. FAMILY VULPECULIDjE 



The only representative of this family (the well-known thresher) is peculiar 

 among sharks for its enormously elongate tail. Its closest affinities otherwise are 

 with the mackerel sharks (p. 35) . 



9. Thresher {Vulpecula marina Valmont) 



Thraser; Swiveltail; Swingletail; Fox shark 



Jordan and Evermann (Alopias vulpes Gmelin), 1896-1900, p. 45. 

 Garman, 1913, p. 30. 



Fig. 10.— Thresher shark ( Vulpecula marina) 



Description. — The thresher is as easily distinguished by its long tail as the 

 hammerhead is by its head, the upper caudal lobe being about as long as the head 

 and body of the fish together, curved much like the blade of an ordinary scythe, 

 and notched near the tip, whereas the lower lobe is hardly longer than the anal 

 fin. It need merely be pointed out in addition that the first dorsal (of moderate 

 size and about as high as long) stands about midway between pectoral and ventral, 

 that the second dorsal and the anal are very small,- the pectoral is very long and 

 sickle shaped, and that the thresher is a stout-bodied shark with short snout, blunt, 

 rounded nose, and small triangular teeth. 



Size. — The thresher grows to a length of about 20 feet or more, fish as large as 

 16 feet in length having several times been taken at Woods Hole. One of 13 feet 

 has been found to weigh about 400 pounds. 



Color. — Dark lead brown to nearly black above; white below, except that the 

 lower sides of the pectorals are leaden in hue. 



General range. — An inhabitant of all warm seas, especially numerous in the 

 Mediterranean and temperate Atlantic. 



