CHARACTERISTICS OF VALUABLE MARINE FISHES 



47 



which is placed in the hinder part of the body, is small and 

 destitute of fin-rays, consisting therefore only of skin and flesh. 

 The tail-fin is less forked than in the herring family ; the lateral 

 line and scales are well developed. The family includes fresh- 

 water species, marine species, and species which like the salmon 

 pass regularly from river to sea and sea to river. The fresh-water 

 .forms are the trout, the grayling, and the various kinds of char. 

 Many kinds of sea trout have been distinguished in different 

 parts of the British Islands, but in the opinion of the late Dr. 

 Francis Day they are connected by intermediate forms with one 

 another and with the fresh-water trout, and so constitute with the 



FIG. 9. The Conger. 



FIG. 10. The Common Eel. 



latter one variable species. The smelt (Fig. 8) is found only in 

 estuaries or near the mouths of rivers, and spawns in brackish 

 water. It is distinguished by its somewhat transparent skin, which 

 is bluish on the back, with a bright silvery band along each side. 

 There are a few species of the salmon family which are entirely 

 marine and live at considerable or even extreme depths in the sea 

 or ocean. One of these marine forms, namely the argentine, is 

 British, having been frequently taken off the west coast of Ireland 

 and Scotland. It is distinguished by the smallness of its mouth, 

 absence of teeth, and the shape of the body, which consists of 

 flat surfaces bounded by longitudinal ridges. The argentine is 

 of no commercial importance in this country. 



