THE SMOOTH HEADS 'AND SOUTHERN SALMON 2867 



THE SMOOTH HEADS AND SOUTHERN SALMON. 

 Families ALEPCCEPHALID^ and HAPLOCHITONID^ 



The first of these two families is typically represented by the genus 

 s Alepocephalus, of which a species (A. niger) is shown in the annexed 

 illustration. While agreeing with the typical salmonoids in the structure 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, tae former occupying the upper front edge of the latter. All the ele- 

 ments 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 blad- 



BLACK SMOOTH HEAD. 

 (One-third natural size.) 



der 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. 



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

 stituting a family which represents the salmonoids in the Southern 

 Hemisphere; the zebra salmon (Haplochiton zebra] being figured as an 

 example of the typical genus. L,ike 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 



