SALMO DEXTEX. 299 



eyes is one and a half times the orbital diameter, and the eye is the same 

 distance from the snout, though the length of the snout varies somewhat with 

 sex and age. The mouth is wide, and the broad maxillary bone extends back 

 below and behind the eyes. 



The teeth are remarkably strong. In the pre-maxillary they have a pre- 

 daceous character, and their length is more than twice the diameter of the scales. 

 The middle teeth in the lower jaw are less developed ; but, as usual, the strongest 

 teeth are on the tongue. The teeth number four to six on each side of the 

 pre-maxillary, thirty in the maxillary, twenty on each side of the mandible, 

 twenty to twenty-one on the palatine bone, five on each side of the tongue, 

 and twenty on the vomer. Four of the vomerine teeth form a transverse row in 

 front, and the remainder make an alternating double row behind ; but the teeth 

 are easily broken off, and gradually replaced, so that the number may vary in 

 different specimens. 



The operculum is large, and extends far back. Its hinder and lower 

 margins form a right angle, but in old males the lower margin becomes 

 curved. The pre-operculum has the lower limb very indistinct. The number 

 of rays on the left varies from twelve to fourteen, and on the right branchio- 

 stegal from eleven to thirteen ; but there are commonly twelve on the right, 

 and thirteen on the left. The rake-teeth on the gill-arches are of moderate 

 length; on the last arch they number six to seven, and are short and blunt. 



The ventral contour forms a flatter arch than the dorsal profile, which is 

 somewhat indented behind the eyes. The dorsal fin begins in front of the 

 middle of the body; it is a little higher than long; its base is equal to half 

 the length of the head, and its last ray is half as long as the longest ray. 

 The rounded adipose fin is opposite the end of the anal fin ; that fin is quite as 

 high as the dorsal ; its base is one-third of the length of the head. The 

 ventral and pectoral fins resemble those of the Common Trout. The caudal fin 

 is emarginate in young specimens, truncate in maturity, and may be rounded 

 in old age. 



The scales resemble those of the Common Trout in size and form. There 

 are thirteen to fourteen scales in a transverse series, descending from behind 

 the adipose fin forward to the lateral line. 



The colour is variable ; sometimes lighter, sometimes darker than Salmo 

 atisonii, but always of a brownish tint on the back, silvery on the sides, and 

 brown on the belly. Old individuals have a dark-brown colour, with coppery 

 metallic lustre, with the belly paler, and throat whitish. There are numerous 

 round spots and irregular markings on the head, and the body is covered with 

 very numerous, small, irregular, black, and often X-shaped dots, which give 

 the young fish a splashed appearance. Everywhere between the black spots are 



