994 CLASS PISCES. 



the most generalised Teleosteans, and those most nearly connected 

 with the bony Ganoids. 



Family Salmonid^e. — The members of this and the next family 

 are so intimately connected by fossil forms, that it is very difficult 

 to draw any distinction between them, and it has accordingly been 

 proposed by some writers that they should be united under the 

 name Halecidtz. The fossil genus Halec is, however, very imper- 

 fectly known, and if it be eventually found advisable to merge the 

 two families, it would seem preferable to employ the name Salmon- 

 idce. in this wider sense. Existing Salmonoids are characterised by 

 the presence of an adipose dorsal fin, and by the premaxilla and 

 maxilla forming the borders of the mouth, and both bearing teeth. 

 There are no scales on the head, and no barbels to the mouth. 

 Recent Salmonoids are either marine, or inhabitants of the fresh- 

 waters of the Northern Hemisphere. Remains of the existing 

 marine genus Osmerus (Smelt) occur in the Upper Greensand of 

 Germany, the Lower Eocene of Glarus, in Switzerland, and the 

 Miocene of Licata, in Sicily ; while nodules of unknown age found 

 in Greenland and Canada enclose a species of Mallotus indistinguish- 

 able from the existing M. villosus of the former region. As forms 

 connecting the Salmonoids with the Clupeoids we may notice Aulo- 

 leflis, Acrognathus, and Osmeroides, from the English Chalk. The 

 first has a rounded body and a depressed head, with minute teeth, 

 and the pelvic fins abdominal. In the second the orbits are of 

 enormous dimensions, and the teeth extremely minute. The third 

 genus (fig. 932) is also abundantly represented in the Chalk of the 

 Lebanon, and appears to have no adipose fin ; its skeleton in many 



Fig. 9-$2.—Osmeroides lewesiensis ; from the Chalk of Sussex. Reduced. 



respects resembles that of the Clupeoids, but the ribs have not the 

 peculiar structure of that group. Sardinius, from the Chalk of the 

 Lebanon, and Sardinoides from the same locality, and also from the 

 Chalk of Westphalia, are more or less closely allied forms ; while 

 Ofiisthopteryx, of the Lebanon Chalk, may also be provisionally 

 placed here. 



Family Clupeid^e. — The existing members of the Clupeoid or 

 Herring family differ from the Salmonoids by the absence of the 



