The Hammer-headed Shark. 421 
fearless of mankind. They follow vessels with great 
eagerness, seizing with avidity everything eatable that 
is thrown overboard ; and have sometimes been known 
to throw themselves on fishermen, and on persons bath- 
ing in the sea. As, however, they are much smaller 
and weaker than most of the other Sharks, they do not 
always attack their enemies by open force, but generally 
have recourse to stratagem. They, consequently, con- 
ceal themselves in the mud, and lie in ambush, like the 
ray or skate-fish, (also one of the cartilaginous fishes,) 
until they have an opportunity of successfully attacking 
their prey. On the coasts of Scarborough, where had- 
docks, cod, and Dog-fish are in great abundance, the 
fishermen universally believe that the Dog-fish make a 
line or semicircle to encompass a shoal of haddocks and 
cod, confining them within certain limits near the shore, 
and eating them as occasion requires : they are there- 
fore considered very destructive to this fishery. The 
flesh of the Dog-fish is hard and disagreeable ; its skin, 
when dried, is made into the well-known shagreen, and 
from the liver a considerable quantity of oil may be 
extracted. Shagreen is also made from the skin of other 
cartilaginous fishes. 
THE HAMMER-HEADED SHARK, (Zygoma malleus,) 
Is a very curious kind, having a transverse head like 
that of a hammer, with an eye at each extremity ; and the 
Fox-Shark, or Thresher (Carcharias vulpes), is remarkable 
for the enormous length of the upper lobe of its tail, 
with which it is able to strike with tremendous force. 
This fish is one of the great enemies of the whale. 
