214 FISHES. 



z dlass. Selensteu 



Fishes.) 



Skeleton more or less ossified; tail homocercal; optic 

 nerves simply crossing, without chiasma; arterial bulb 

 simple, with two opposite valves at its origin; air 

 bladder, if present, not lung - like ; body usually scaly, 

 sometimes covered with naked skin or bony plates; 

 membrane bones (opercles, etc.) developed in relation to 

 the skull. This group comprises the great majority of 

 recent fishes. 



OEDEE Z.-TELEOCEPHALI 



(The Typical FisTies.) 



This order again comprises the vast majority of recent 

 fishes, and is characterized rather negatively, as wanting 

 the peculiarities of the other orders than as having any 

 positive distinctions of its own. The maxillaries are 

 normally developed and distinct from each other, never 

 forming the base of a long barbel. The gills are pecti- 

 nated and of the ordinary pattern, and the gill-openings 

 are in front of the pectorals and never very narrow; the 

 subopercle is present. The scales are (when present) 

 very rarely ossified, and are generally either ctenoid or 

 cycloid. This group includes the Acanthopterygians 

 and Malacopterygiam of Cuvier, and the nearly cor- 

 responding Ctenoidei and Cycloidei, Physoclysti and 



