49 2 
TUBE-BLADDERED GR O UP. 
of the skull and the presence of two true tail-vertebrae, as well as in other features, 
these fish may be distinguished by the absence of the fatty fin. Whereas barbels 
are invariably absent, and the head is always naked, the body may be either scaled 
or bare. Both premaxillae and maxillae enter into the formation of the margin of 
the upper jaw, the former occupying the upper front edge of the latter. All the 
elements of the gill-cover are present; the dorsal fin is situated opposite the anal 
in the caudal region; the gill-openings are very wide; false gills are present; the 
air-bladder is wanting; and the curved stomach has no blind appendage. All 
these fish have the teeth feebly developed, the eye large, and the bones thin; while 
they are remarkable for their uniformly black coloration. The whole of them are 
deep-sea fishes, with an apparently almost cosmopolitan distribution, some of them 
having been taken at a depth of over two thousand fathoms. Whereas the body 
of the typical genus is covered with thin cycloid scales, in another type the place of 
these is taken by fine granules. 
ZEBRA-SALMON. 
By this name mav be designated two genera of fresh-water fish, 
Southern Salmon. . J v ® ” ’ 
constituting a family which represents the salmonoids in the Southern 
Hemisphere ; the zebra-salmon (Haplochiton zebra ) being figured as an example of 
the typical genus. Like the salmon and herrings, devoid of barbels, these fish 
agree with the former in the presence of a fatty fin, but differ in having the margin 
of the upper jaw formed solely by the premaxillary bones. The body may be 
either naked or covered with scales: the gill-opening is wide; false gills are 
present; and the air-bladder is simple. The ovaries are in the form of plates, and, 
in the absence of a duct, the eggs fall into the abdominal cavity. The species of 
the typical genus, which, although devoid of scales, are externally very similar in 
appearance to trout, are confined to the lakes and rivers of Chili and the extreme 
south of Patagonia and the Falkland Islands. In South Australia and New 
Zealand the family is represented by the genus Prototroctes, in which the body is 
scaled and the jaws are armed with minute teeth; the New Zealand species being 
commonly known to the colonists as the grayling. 
