2850 



THE BONY FISHES AND GANOIDS 



SECTION ISOSPONDYLT 

 THE FEATHER BACKS Family NOTOPTERID^ 



According to the classification we are following, the whole of the remaining 

 members of the tube-bladdered fishes form a group denominated Isospoudyli, and 

 characterized as follows: The parietal bones are completely separate; the sym- 

 plectic bone, which is wanting in the group last treated of, is present; the anterior 

 vertebrae are simple and unmodified, and both the upper and lower pharyngeal 

 bones are separate. The group includes the least specialized of all the bony 

 fishes, and those forming a transition to the ganoids. From the peculiar form of 

 the dorsal fin certain fresh- and brackish-water fishes from West Africa and the 



BORNEAN FEATHER BACK. 

 (One-third natural size.) 



Oriental region, one of which (Notopterus) borneensis is shown in the above illus- 

 tration, have received the not inappropriate name of feather backs. They consti- 

 tute a family differing from all the others in this section by the tail being tapering 

 and fringed inferiorly by a continuation of the anal fin, as well as by the presence 

 of a cavity in the ring-like pterotic bone, the base of the skull being double. Both 

 the body and the head are covered with small scales; barbels are wanting; the 

 margin of the upper jaw is formed in front by the premaxillae and at the sides by the 

 maxillae; and the opercular bones are incomplete. There is no fatty fin, and the 

 dorsal, when present, is very short, and situated in the caudal region; the pelvic 

 pair being rudimental or wanting. The air bladder is divided internally into several 

 compartments and terminates at each end in a pair of narrow prolongations, of 

 which the anterior ones are in communication with the organ of hearing. A further 



