2862 THE BONY FISHES AND GANOIDS 



set in sockets, and a single series of similar teeth in the lower jaw, the palatine 

 bones being toothless. A peculiarity of the vertebrae of these fishes, with the 

 exception of those of the neck, is the presence of two deep grooves and pits on their 

 sides. Some of these fish attained huge dimensions; the American and Australian 

 Cretaceous genus Portheus being distinguished by the presence of an enormous bony 

 crest in the middle line of the skull. 



THE HERRING TRIBE Family CLUPEID^E 



Second to none in their commercial importance, the herring tribe are remark- 

 able for the enormous number of individuals by which several of the species are 

 represented rather than for the multiplicity of the species themselves; this being 

 probably one of the chief reasons for the great value of these fishes as a food sup- 

 ply. Although the existing representatives of the family may be readily dis- 

 tinguished from the salmonoids by the absence of a fatty fin, yet extinct forms 

 indicate such an intimate connection between the two groups as to induce some 

 naturalists to include both in a single family. Whatever may be the ultimate ver- 

 dict on this point, in a work like the present, where we are mainly concerned with 

 living types, it is obviously preferable to follow the ordinary system. While the 

 typical representatives of the family have the parietal bones of the skull separated 

 by the supraoccipital and but one true tail vertebra, in the genus Rlops the parietals 

 are in contact, and there are two caudal vertebrae. On this account it has been 

 proposed to make the latter genus the type of a distinct family; a similar proposal 

 having been made in the case of an analogous departure from the ordinary type 

 among the salmonoids. In addition to the absence of the fatty fin, most herrings 

 are characterized by the presence of small bony plates on the lower margin of the 

 body. Externally the whole body is scaled, with the lateral line mostly wanting; 

 while the head is generally naked, and the muzzle always without barbels. The 

 under surface is more or less compressed, and generally so much so as to form a 

 sharp edge which is usually serrated. In the gill cover the four elements are 

 present, and the gill openings are in most cases very wide. Both premaxillae and 

 maxillae enter into the formation of the margin of the upper jaw, but each of the 

 latter bones is peculiar in being composed of three separate pieces. The single 

 short dorsal fin has a small or moderate number of weak rays, and the anal may be 

 many-rayed. The stomach is furnished with a blind sac; the air bladder is of more or 

 less simple structure; and well-developed false gills are usually present. Distributed 

 over all temperate and tropical seas, herrings are mainly littoral fishes, none of them 

 being inhabitants of deep water, and none truly pelagic. Although the majority 

 are marine, many of them will enter fresh water, and some live permanently therein, 

 while it is probable that all can be acclimatized to such conditions. As might have 

 been expected from their generalized structure, herrings are an ancient group, the 

 typical genus dating from the period of the Chalk, while anchovies and other exist- 

 ing generic types are known from the Eocene. A number of more or less allied Cre- 

 taceous genera appear to connect the family very closely with the higher ganoids. 



