SALMONID^] 115 



is likewise slightly more strongly developed in some than it is in others. The 

 lower jaw in some varieties, as the torgoch of Wales, may be longer anteriorly 

 than the upper jaw. The opercular pieces are of as diverse shapes in the charr as 

 described in the trout, and frequently are dissimilar in the opposite sides of the 

 head. Teeth present in the jaws and in a line across the vomer near its anterior 

 extremity, and opposite the teeth of the palatine arch, none along the body of the 

 vomer. Fins dorsal usually commences about midway between the end of the 

 snout and the base of the caudal fin, in some examples a little nearer the snout. 

 The pectoral and other fins are of varying lengths in accordance with locality, 

 sex, and other varying conditions. Scales small and a much larger number of 

 rows descending from the back of the lateral-line, than there are of pierced rows 

 along its whole extent (see below). Cuecal appendages these vary considerably, 

 in Loch Inch 38 (Thompson) ; L. Rannoch, 28 ; the Lakes, 28-44, Dr. Giinther 

 detected from 36 to 52, and the smallest number in those from Windermere, 36, 

 from the same locality I possess an example with 28, and found the same number 

 in a specimen received as $. struanensis. It is evident they are as inconstant as in 

 the trout. Colours these again vary, but as a general rale the belly, prior to 

 spawning, becomes of a crimson or claret colour, while there are generally some 

 light-coloured orange or black spots on the body and head. The front edge of the 

 dorsal, ventral, and caudal as well as the upper edge of the pectoral are often of a 

 pare white or orange colour. The variation in tints and shades are not so great 

 as in the trout (see page 109). In some, the ventral, anal, lower portion of 

 the pectoral, and hind edge of the caudal partake of the scarlet colour of the 

 abdomen. 



Varieties in colour. " By such alone," observes Dr. Giinther, " fresh specimens 

 of Salmo salvelinus and S. umbla, of S. Grayii and S. Willughbii, may be always 

 distinguished," and in his interesting division of the British species into many, he 

 divides it first in accordance with the development of the jaws and size of the 

 teeth, an inconstant character, as I have observed (page 109). It is then sub- 

 divided in respect to the length of the pectoral fins : but here it is evident that 

 the question of sex, locality where hatched and reared, and many other local 

 circumstances, must be taken into consideration. I examined eight specimens 

 received from the lakes, and found as follows : All were from 8^- to 9 inches in 

 length ; in two the pectoral extended just half the distance to the base of the 

 ventral, and in the remainder If, 1 T 3 T , l|i, If, 2 T \-, and 2^ in the interspace, 

 clearly showing that this is not a character on which too much reliance should be 

 placed. 



The next subdivision is into whether the dorsal fin contains 13 or 14 rays. 

 Such an enumeration is evidently open to uncertainty, unless it is taken into 

 consideration and recorded how many undivided and how many branched rays are 

 present. The first few which are undivided are minute, one or two may even be 

 wanting. Thus in the 8 examples from the same locality already referred to I 

 found from 3 to 4 undivided, and 9 to 10 divided rays in the dorsal fin, and 

 similarly in the anal, 3 to 4 undivided and 8 to 9 divided rays. Moreau, in 

 France, finds D. ^ s 5 , A. -flf. This character, therefore, is unreliable. 



As to the comparative height of the body that varies with sex, season and food, 

 and cannot be otherwise than a very uncertain element in the discrimination of a 

 species. 



As regards external characters, Dr. Giinther observed (1862) that " dried and 

 stuffed specimens of charr are of little or no use." One would have supposed from 

 this that the colours, scales, and size of the fins would afford no criterion as to 

 species. In 1864 the same author remarked that" the difference in the size of the 

 scales is one of the most constant and important characters in salmonoids." 



In examining numerous examples of Salmo fontinalis reared in this country, 

 one cannot resist being struck with the considerable differences which occur as to 

 the number of the scales, and the consequent inconstancy of this factor as a 

 criterion for-species. Taking the pierced scales along the lateral-line, I possess 

 specimens which have from 122 to 142 : but it is in the number of irregular rows 

 which descend from the back to the lateral-lino where the greatest diversitv occurs, 



8 * * 



