476 



TUBE-BLADDERED GROUP. 



characterised as follows. The parietal bones are completely separate ; the 

 symplectic 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 specialised 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 



BORNEAN FEATHER-BACK (J nat. Size). 



West Africa and the Oriental region, one of which (Notopterus borneensis) 

 is shown in the illustration herewith, have received the not inappropriate name 

 of feather-backs. They constitute 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 com- 

 partments, 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 

 peculiarity is that the spawn falls into the cavity of the abdomen previous to its 

 exclusion. There are two Indian representatives of the genus, one of which grows 

 to a couple of feet in length; a third is Bornean, and the other two are West 

 African. An extinct species has been described from the Eocene of Sumatra. 



THE SOUTHERN PIKELETS, Family 



For want of a better name we may designate by the name of southern pike- 

 lets a genus of small fresh-water fishes from the Southern Hemisphere, one of which 

 (Galaxias attenuatus) is represented in the lower figure of the illustration on 

 p. 475. Together with the members of the next family, these fishes are dis- 

 tinguished from the other genera of the present sectional group noticed here by 

 having the base of the cranium simple, the tail being rounded or forked, and the 



