SELACHOIDEI. 315 



offer them abundance of food; wliilst the majority of the 

 smaller kinds are shore fishes, rarely leaving the bottom, and 

 sometimes congregating in immense numbers. The move- 

 ments of sharks resemble in some measure those of snakes, 

 their flexible body being bent in more than one curve when 

 moving. 



Sharks are most numerous in the seas between the 

 Tropics, and become scarcer beyond, a few only reaching the 

 Arctic circle ; it is not known how far they advance south- 

 wards towards the Antarctic region. Some species enter fresh 

 waters, and ascend large rivers, like the Tigris or Ganges, to 

 a considerable distance. The pelagic as well as the shore 

 species have a wide geographical range. Very few descend 

 to a considerable depth, probably not exceeding 500 fathoms. 

 There are about 140 different species known. 



Sharks have no scales like those of other fishes; their 

 integuments are covered with calcified papilla which, under 

 the microscope, show a structure similar to that of teeth. If 

 the papillae are small, pointed, and close set, the skin is 

 called " shagreen ; " rarely they are larger, appearing as 

 bucklers or spines, of various sizes. 



These fishes are exclusively carnivorous, and those armed 

 with powerful cutting teeth are the most formidable tyrants of 

 the ocean. They have been known to divide the body of a 

 man in two at one bite, as if by the sweep of a sword. 

 Some of the largest sharks, however, which are provided 

 with very small teeth, are almost harmless, feeding on small 

 fishes only or marine invertebrates. Others, particularly of 

 the smaller kinds, commonly called " Dog-fishes," have short 

 or obtuse teeth, and feed on shells or any other animal sub- 

 stance. Sharks scent their food from a distance, being readily 

 attracted by the smell of blood or decomposing bodies. 



In China and Japan, and many other eastern countries, 

 the smaller kinds of sharks are eaten. Sharks' fins form in 



