492 



TUBE-BLADDERED GROUP. 



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 premaxillse 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. 



Southern Salmon. 



ZEBRA-SALMON. 



By this name may be designated two genera of fresh-water fish, 

 '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 cavit} r . 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. 



