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 vertebrse 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 liat. 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 premaxillse 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 Galaxiibje. 
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 
(Gcilaxias 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 
