B ASKING-SHARKS. 
5 2 7 
which more than half is taken up by the tail, this shark has the second dorsal and 
anal fins very small; the caudal fin extremely elongated, and without a pit at its 
root; no keel on the sides of the tail; and the teeth, which are similar in both 
jaws, of small size, compressed and triangular, with smooth edges. Like most 
sharks, the thresher has a wide range, being abundant throughout the Atlantic and 
Mediterranean, and also found off the coasts of New Zealand and California. The 
comparatively small size of its teeth indicates that it is not adapted for killing- 
large prey; and, as a matter of fact, this shark chiefly feeds upon the various 
species of the herring tribe and mackerel, among which it inflicts terrible destruc¬ 
tion. It derives its name of thresher from its habit of beatino- the water with its 
O 
long tail in order to drive the members of the shoals on which it preys into a 
compact mass, when they can be the more readily seized; and its voracity may be 
inferred from the fact of no less than nineteen mackerel and two herrings having- 
been taken from the stomach of a single individual. It is commonly reported by 
sailors that threshers, in company with killers and sword-fish, make attacks on whales 
by leaping high in the air and belabouring the unfortunate cetaceans with powerful 
blows of their tails as they descend; but these statements have been generally 
discredited by naturalists, apparently on the ground that the teeth of these sharks 
are not adapted for rending the flesh of large animals. It is, however, somewhat 
difficult on such grounds to refuse to believe the circumstantial accounts we 
possess, and it may be that the threshers join in the fray in order to feed on the 
smaller fragments left by their more powerfully armed coadjutors. 
The largest of the North Atlantic members of the suborder is 
the basking-shark (Cetorhinus maximus), which now alone represents 
a genus with the second dorsal and anal fins very small, a pit at the root of the 
caudal fin, a keel on each side of the tail, the gill-clefts very large and wide, 
and the teeth very small, numerous, and conical, without basal cusps, and seldom 
serrated at the edges. This shark, which grows to a length of over 30 feet, is 
regularly hunted on the west coast of Iceland for the sake of the oil from its liver, 
of which a single fish may yield considerably more than a ton. It derives its 
name from its habit of lying motionless during calm, warm weather on the surface 
of the water, with the tall first dorsal fin and a considerable portion of its back 
exposed; several individuals often consorting together. The gill-arches are provided 
with very long rakers bearing granular tooth-like structures; and in the young 
the muzzle is relatively longer and more pointed than in the adult. Unless 
attacked, when it can inflict blows with its tail capable of staving in the sides of 
a boat, this shark is perfectly harmless, its food consisting entirely of small fishes 
which swim in shoals, and various invertebrates. Remains of an extinct species 
occur in the Pliocene deposits of Belgium, while others from older Tertiary beds 
have been tentatively assigned to the genus. 
Basking-Shark. 
Indo-Pacific Basking-Shark,—F amily Rhinodontidje. 
Although resembling the true basking-shark in the large size of its gill-clefts 
and the structure of its gill-rakers, the gigantic species (Rhinodon typicus ) figured 
in the illustration on p. 528 differs in having the mouth and nostrils situated 
