454 FISHES CHAP. 



the eastern and southern coasts of England. The Fish is 

 gregarious in its habits, often swimming in shoals near the 

 surface. The name " Basking Shark " has been suggested by 

 its habit of lying motionless on the surface in warm or calm 

 weather, as if basking in the sun, with its dorsal fin protruding 

 from the water. Unless attacked, this Shark is quiet and 

 inoffensive. It derives its food-supply from small pelagic Fishes, 

 and also from marine Invertebrates, which are strained from the 

 water by the fringes of long, slender gill-rakers with which 

 the branchial arches are provided. At one time harpooned 

 and caught off the Irish, Scotch, and Norwegian coasts for the 

 sake of the oil obtained from its liver, the Fish is now of little 

 economic importance. Nothing is known of its mode of repro- 

 duction. 



Extinct species of Cetorhinus have been founded on detached 

 vertebrae and isolated teeth from deposits of Pliocene age in 

 Belgium and Italy, and possibly from still earlier Tertiary 

 formations. Dermal spines similar to those found on the 

 claspers of the males in the existing species occur in the Antwerp 

 Crag, and in the Red Crag of Suffolk. 



Fam. 12. Rhinodontidae. Two dorsal fins, without spines, 

 the anterior a little in front of the pelvic fins, the second opposite 

 the anal. Tail with lateral keels and a pit at its root. Spiracles 

 small. Nictitating membranes absent. Mouth and nostrils 

 nearly terminal. Teeth very minute, numerous, and conical in 

 shape. 



One genus, Rhinodon, with one or two species, is known. These 

 Sharks are very widely distributed, specimens having been seen 

 or captured in the neighbourhood of Ceylon, at the Seychelles, 

 the Cape of Good Hope, Callao on the Peruvian coast, in the 

 Gulf of California, and off the coast of Florida. Rhinodon is 

 probably the largest known Shark. It is stated to exceed 50 

 feet in length, but to be quite harmless. Scarcely anything is 

 known of its habits, but the small size of the teeth, and the 

 length of the gill-rakers, which resemble those of the Basking 

 Shark, suggest a similar kind of food. 



Fam. 13. Spinacidae. -Two dorsal fins, the first in advance 

 of the pelvic fins. Anal fin absent. Nictitating membrane 

 absent. Spiracles rather large. Vertebrae cyclospondylic. Teeth 

 variously modified in different genera. 



