166 THE ANATOMY OF VEETEBEATED ANIMALS. 



1. The Physostomi. — This group contains the Siluroidei, 

 the Cyprinoidei. the Characini, the Cyprinodontes,t}ie Sahnon- 

 idce, the Scopelini, the Esocini, the Mormyri, the Galaxiae, 

 the Clupeidx, the Heteropygii, the Munenoidei, Symbranchii, 

 and Gymnotini. The air-bladder is almost always present, 

 and, when it exists, has an open pneumatic duct. The skin 

 is either naked, or provided with bony plates, or cycloid 

 scales ; the ventral fins, when present, are abdominal in 

 position. The fin-rays (except in the pectoral and dorsal 

 fins of sundry Siluroidei) are all soft and jointed. The 

 inferior pharyngeal bones are always distinct. 



In all other Teleostean fishes the air-bladder is either 

 absent, or devoid of an open pneumatic duct. Hence they 

 are termed, collectively, Physoclisti by Haeckel. 



2. The Anacanthini. — The body has cycloid or ctenoid 

 scales, or is naked. The ventral fins, if present, are jugular 

 in position. The fin-rays are aU articulated. The inferior 

 pharyngeal bones are distinct. [Ophidini, Gadoidei, Pleuro- 

 iiectidce. ) 



The PleuronectidcB are the most aberrant of all Teleostean 

 fishes, on accoiint of the disturbance in the bilateral sjon- 

 metry of the body, skiill, and fins, to which reference has 

 already been made (p. 30). 



3. The Acanthopterl have generally ctenoid scales, thoracic 

 or jugular ventral fins, entii-e fin-rays in some of the fins, 

 and distinct inferior pharyngeal bones. The Percoidei, Cata- 

 phracti, Sparoidei, Scicenoidei, Labyrinthici, Mugiloidei, Nota- 

 canthini, Scomberoidei, Squamipennes, Tcenioidei, Gobioidei, 

 Blennioidei, Pediculati, Theuthyes, and Fistulares, belong to 

 this great group. 



4. The Pharyngognathi is the name given by MuUer to a 

 somewhat artificial assemblage of fishes, the only common 

 chai-acters of which are the ankylosis of the inferior pha- 

 ryngeal bones and the closed pneumatic duct. They have 

 either cycloid, or ctenoid, scales. The ventral fins may be 

 abdominal or thoracic. The anterior dorsal and ventral 

 fin-rays may be either unjointed, as in the Labroidei, Poma- 

 centridcB, Chromidce ; or articulated, as in the Scomberesoces. 



