CHAPTER VII. 

 THE SKELETON OF THE CODFISH 1 . (Gadus morrhua.) 



I. EXOSKELETON. 



The exoskeleton includes 



(1) Scales. These are of the type known as cycloid 

 and consist of flat rounded plates composed of concentrically 

 arranged laminae of calcined matter, with the posterior margin 

 entire. The anterior end of each scale is imbedded in the skin 

 and is overlapped by the preceding scales. 



(2) The teeth. These are small, pointed, calcified struc- 

 tures arranged in large groups on the premaxillae, mandible, 

 vomer, and superior and inferior pharyngeal bones. 



(3) The fin-rays. These are delicate, nearly straight 

 bony rods which support the fins. 



II. ENDOSKELETON. 



The endoskeleton of the Codfish, though partially carti- 

 laginous, is mainly ossified. 



It is divisible into an axial portion, including the skull, 

 vertebral column, ribs, and skeleton of the median fins, and 

 an appendicular portion, including the skeleton of the 

 paired fins and their girdles. 



1. THE AXIAL SKELETON. 

 A. THE VERTEBRAL COLUMN. 



This consists of a series of some fifty-two vertebrae, all com- 

 pletely ossified. 



1 See T. J. Parker's Zootomy, London, 1884, p. 86. 



02 



