Osteichthyes is a class of fishes where exoskeleton is bony.. Glills are covered by operculum, ventral heart, belongs to the phylum chordata. eg : Hippocampus, catla etc...
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The characteristics are as follows :- 

⇒ It includes both marine and fresh water organisms wid bony endoskeleton.
⇒ Their body is streamlined and mouth is terminal.
⇒ They have four pairs of gills which are covered by operculum on each side.
⇒ Air bladder is present which regulates buoyancy.
⇒ Two chambered heart.
⇒ Cold-blooded and are uni-sexual..
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