CHAPTER VI. 



THE TEETH OF FISHES. 



IN the following pages nothing more than a brief account 

 of a few typical forms can be attempted ; the limits of space 

 forbid the mention of many creatures, or the insertion of 

 detailed descriptions of the dentition even of the few which 

 are included in its pages. In the class of fish the task of 

 selection of the forms for description is no easy one ; for 

 the almost infinite diversity of dentition which exists in 

 it makes it a matter of peculiar difficulty to frame any 

 general account, or to do more than present before the 

 reader a description of a few individual forms from which he 

 may gather, as. best he can, a general idea of piscine 

 dentition. 



Fish may be grouped into 



I. PHARYNGOBRANCHII. IV. GANOIDEI. 



II. MAESIPOBEANCHII. V. TELEOSTEI. 



III. ELASMOBEANCHII. VI. DIPNOI. 



I. PJiaryngobranchii comprise only the Amphioseus, 

 II. Marsipobra/neMi comprise the Lampreys and the parasitic 

 Myxine. 



III. Elasmobra/nohii comprise the Sharks and Rays (Plagiostom-i) 



and the Chimera and its allies (Holocepliali). Their skele- 

 tons are cartilaginous, with an ossified crust. 



IV. Ganoldei. A large number of extinct fish of existing- fish the 



Lepidost&us, or Bony Pike, is the most familiar. 

 V. Tcleostei comprise the ordinary Fish in our seas and rivers. 

 VI. Dipnoi. The Lepidosireng, or Mud Fishes, capable of living for 

 a long time in moist mud. 



The Marsipobranchii need not detain us long ; they are 



