SALMO SALVELIXUS. 319 



than twice its diameter from the snout, and more than twice its diameter from 

 the other eye, so that the frontal interspace is broad. The gape of the mouth 

 is wide ; the maxillary bone usually reaches back for fully half the length of 

 the head. Both jaws are equal, or, if there is any inequality, the lower is the 

 shorter (Fig. 161). 



The teeth are in a single row in the pre-maxillary, maxillary, palatine 

 bones, and lower jaw. Those in the maxillary bone are comparatively small. 

 The tongue is not toothed at the edges, but a double row of teeth, parted 

 by a deep furrow, extends along- the middle. The hyoid bone has a simple 

 longitudinal row of teeth. The dentition of the vomerine plate is very 

 variable; generally there are six or seven teeth arranged in a nearly equal -sided 

 triangle, with its apex directed backwards, or there may be a simple transverse 

 row, or two longitudinal rows, with nine teeth in each. 



The operculum is rounded. There are usually ten branchiostegal rays on the 

 right side, and eleven on the left, though there are occasionally ten on both sides. 

 The rake-teeth of the gill-arches are thin, long, and finely denticulated. 



The dorsal profile is much more convex than the ventral contour. The 

 dorsal fin commences rather in front of the middle of the length. It is 

 about two-thirds of the height of the body. It is truncated, but the trun- 

 cation scarcely reduces the height of the last rays one-half. The adipose fin is 

 opposite to the end of the anal fin. The latter is as high as the dorsal, bnt 

 more truncate behind. The ventrals are opposite the hinder part of the dorsal. 

 They are well developed, their longest rays being equal to those of the anal. 

 The terminal rays of the forked caudal are a little longer than the pectoral 

 fin, and are from one-seventh to one-sixth of the length of the fish. 



The scales are very minute, delicate, and firmly attached to the skin. 

 They are smallest and most elongated on the throat and belly, and largest 

 on the sides, where they are more circular. 



The lateral line is straight, and nearer to the liaek than the abdomen. It 

 comprises from one hundred and twenty-four to one hundred and thirty simple 

 pores, although there are generally over two hundred and twenty scales in the 

 lateral line, but only every second scale is perforated. Among the cephalic 

 canals the lower jaw has the pores most distinct. 



The numl)er of pyloric appendages is from thirty to forty. All are mode- 

 rately long, and none exceed the length of those forming the first circle. 



The colour is almost as variable as that of the Common Trout. In the 

 living fish at spawning-time the upper part of the head and back are brownish- 

 green, the sides of the body lighter, and the lower jaw is yellowish-white. The 

 under side passes through all shades of orange to vermilion, from the throat to 

 behind the ventral fins, the colour being most brilliant in front of the ventrals. 



