HOLOCEPHALI OR CHIMERAS. 261 



SUB-SECTION III. 



THE ORDER OF HOLOCEPHALI OR CHIM.ERAS. 



THE Holocephali or Chimseras are fishes of very 

 remarkable form and structure. They are more or less 

 allied to the Sharks, especially in the nature of their 

 branchiae, which have the same structure as those of the 

 latter, but the five passages which carry the water from 

 the branchial chambers of the Chimseras unite so as to 

 form only one external opening ; and this opening is 

 covered by a rudimentary operculum. 



The Chimaeras have no upper jaw, the four upper 

 teeth being supported upon the front of the skull ; and 



Fir,. 300. 



Northern Chinifera or King of Herrings, Chimcera monstrosa. 



they have only two teeth in the lower jaw. They have 

 no backbone, the vertebral column being represented only 

 by a chorda-dorsalis (see page 32). These fishes are three 

 or four feet in length and belong to the cold regions. 



The name Holocephali comes from the Greek holos, 

 whole, and Tcephale, the head. 



