CHAPTER LXVI 



ORDER OF SHARKS 



SQUAU 



WE have now reached the Subclass of Cartilaginous 

 Pishes. 



And what is a "car-ti-lag'i-nous fish?'' 



Cartilage is a bloodless tissue, commonly called gristle, 

 flexible but not elastic, quite colorless, of the consistency of 

 cheese-rind, and of use in the anatomy of animals for sustain- 

 ing or connecting softer parts. The external ear of man con- 

 sists chiefly of a convoluted wing of cartilage covered with 

 skin. The so-called 'breast-bone" of man is a tree-like 

 development of cartilage designed to bridge together the 

 outer ends of the principal ribs, protect with some firmness 

 the vital organs within and yet permit the rise and fall of the 

 chest in breathing. 



The Cartilaginous Pushes, embracing the sharks, rays, 

 skates and intermediate forms, are those whose skeletons are 

 largely composed of plates and stems of cartilage, or gristle, 

 and but little bone. Instead of bony rays, the fins of these 

 creatures are supported by cartilaginous rays so closely joined 

 together that they form plate-like structures. 



General Characters of Sharks. — With few exceptions, 

 sharks have externally the same general form as the typical 

 fishes. Instead of broad, flat scales that overlap each other 

 like shingles, their scales are very minute, horny, sharp-pointed 



30S 



