10 



FISHES. 



yet in some of the Spiny-finned Fishes they 

 possess much hardness. In one large division, 

 including the Sharks and Rays, the skeleton is 

 composed of gristle or cartilage instead of bone. 



ik „. 



SKELETON OF HADDOCK. 



The vertehrce, or joints of the spine, are excavated 

 at each end in a conical cavity ; the hollow thus 

 formed between every joint and its neighbour is 

 filled with a jelly-like substance, which is con- 

 tinuous through the whole spine, by means of a 

 hole pierced through the centre of each vertebra. 

 There is no true spinal marrow. In general, the 

 tubular perforation is small, but in many of the 

 Gristly Fishes it is of so great a diameter as to 



reduce the vertehrcE to mere cartilaofinous rinses. 

 ... . 



The vertehrt^ give origin to spinous processes, 



both above and below, for the attachment of 



muscles. Within the cavity of the belly the 



lower processes are wanting, and are replaced 



by lateral ones, to which the ribs are attached. 



These are commonly numerous, slender, flexible 



bones, each of which sends oflf a branch of almost 



equal length and tenuity ; some species, as the 



