2 9 02 SHARKS AND RAYS 



date. Observations are still required as to the mode of life and breeding habits of 

 Rondeleti's shark. Two other species of large sharks constitute the genus Odon- 

 taspis. With teeth almost indistinguishable from those of the porbeagles, these 

 species differ by the second dorsal and anal fins being nearly as large as the first 

 dorsal, and the absence of a pit at the root of the caudal fin, and of a keel on the 

 sides of the tail. 



Another species not uncommonly met with in British waters is the 

 fox shark or thresher (Alopecias vulpes) , the sole representative of its 

 genus, and easily recognized by the inordinate length of the upper lobe of its tail 

 fin, from which it derives its name. Growing to a length of fifteen feet, of 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 Mediter- 

 ranean, and also found off the coasts of New Zealand and California. The compar- 

 atively small size of its teeth indicates that it is not adapted for killing large prey; and, 

 as a matter of fact, this shark feeds chiefly upon the various species of the herring 

 tribe and mackerel, among which it inflicts terrible destruction. It derives its 

 name of thresher from its habit of beating the water with its 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 that 

 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 com- 

 pany with killers and swordfish, make attacks on whales by leaping high in the air 

 and belaboring the unfortunate cetaceans with powerful blows of their tails as they 

 descend; but these statements have been generally discredited by naturalists, appar- 

 ently 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 power- 

 fully armed coadjutors. 



The largest of the North Atlantic members of the suborder is the 

 Baskmg Shark 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 ser- 

 rated at the edges. This shark, which grows to a length of over thirty feet, is 

 regularly hunted on the west coast of Ireland 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, 



