THE LIVING WORLD. 
75 
Whether the pilot fish really acts as a guide for tbe shark is disputed, but it 
is asserted that pilot fish have been known to find the bait, and without touching 
go in search of its voracious companion. Moreover, cases are mentioned where 
the pilot fish repeatedly steered the shark away from a baited hook. The pilot 
fish resembles the mackerel; its silvery gray color being similarly relieved by 
five dark-blue transverse bands. 
The Porbeagle, or Mackerel Shark, (. Lamna cornubica ) is a great annoy¬ 
ance to mackerel fishermen, as it breaks their lines and carries off both bait 
and hooks. 
The Basking Shark ( Cetorhinus maximus) is frequently seen in schools, 
whose backs rise above the surface, and whose great length makes them appear 
formidable, although they do not voluntarily attack men, and even when irritated 
only occasion damage, as the whale does, by powerful blows struck by their tails. 
The Thresher Shark 
(.Alopias vulpes ) is specially 
remarkable for its long tail, 
which frequently is nearly 
as long as the body. It is 
bluish in color and has a 
white belly. It is a great 
destroyer of herring and 
mackerel, and while feeding 
upon its prey lashes or 
threshes the water with its 
tail, apparently with the 
object of keeping the fish 
herded. 
The Smooth Hound, 
Sea Hound, or Dog Shark 
(Mustelis cam's) is sometimes 
called the hammerhead , but 
is only a few feet in length, 
and must not be confounded 
with the true hammerhead 
(.Zygcena malleus) ; is harm¬ 
less, feeds upon mollusks, 
and has received its popular 
name from its outward re¬ 
semblance to the true dog-fish. The true hammerhead is supposed to be a 
man-eater, though finding parts of a human body in the stomach of one speci¬ 
men does not prove absolutely that it killed the man. It reaches a length of 
twenty-five feet, and its head'consists of a double hammer-like projection, each 
extremity of which is surmounted by an eye. 
The Great Blue Shark {Carcharinus glaucus). It is found in every sea, 
is blue above and white below, and reaches the length of more than twenty feet. 
The Swell Shark ( Scyllium ventricosum) , is so called not because of his 
apparel, but because he will, when caught, swallow air until swollen out of all 
proportion. It is found on the Pacific coast of Mexico—a land abounding in 
curiosities, as well as rich in products valued by mankind. 
BASKING SHARK. 
