PHYLOCENY. 



107 



specialization of the superior pharyngeal bones, which 

 is continued by the Haplodoci (Batrachidae). This 

 cannot be called a degenerate line, although the fin- 

 rays are soft. 



The double bony floor of the skull of the distegous 

 percomorph fishes is a complication which places them 

 at the summit of the line of true fishes. At the sum- 

 mit of this division must be placed the Pharyngogna- 

 thi, which fill an important role in the economy of the 

 tropical seas, and the fresh waters of the Southern 

 Hemisphere. By means of their powerful grinding 

 pharyngeal apparatus they can reduce vegetable and 

 animal food inaccessible to other fishes. The result 

 is seen in their multifarious species and innumerable 

 individuals decked in gorgeous colors, and often reach- 

 ing considerable size. This is the royal suborder of 

 fishes, and there is no reason why they should not con- 

 tinue to increase in importance in the present fauna. 



Very different is the line of the Plectognathi. The 

 probable ancestors of this division, the Epelasmia 

 (Chaetodontidse, etc.), are also abundant in the tropi- 

 cal seas, and are among the most brilliantly colored of 

 fishes. One of their peculiarities is seen in a shorten- 

 ing of the brain-case and prolongation of the jaws 

 downward and forward. The utility of this arrange- 

 ment is probably to enable them to procure their food 

 from the holes and cavities of the coral reefs, among 

 which they dwell. In some of the genera the muzzle 

 has become tubular (Chelmo), and is actually used as 

 a blow-gun by which insects are secured by shooting 

 them with drops of water. This shortening of the 

 basicranial axis has produced a corresponding abbre- 

 viation of the hyoid apparatus. The superior pharyn- 

 geal bones are so crowded as to have become a series 



