1. SALMO. 139 



distcancc between the posterior margin of the orbit and the end of 

 the operculum, Tlie top of the profile of the head is scarcely elevated 

 above the margin of the orbit, the diameter of which is one-fifth of 

 the length of the head, somewhat shorter than the snout, and two- 

 thirds of the width of the interorbital space : the latter is but very 

 slightly convex, with a very indistinct ridge along the middle. The 

 nostrils are situated midway between the end of the snout and the 

 orbit. The maxillary extends scarcely to the vertical from the poste- 

 rior margin of the orbit, and is armed with from thirteen to seven- 

 teen very small teeth. AU the other teeth are small ; four to six in 

 the intermaxillary, fifteen in each mandible, three on the vomer, 

 fifteen on each palatine, and four pairs on the tongue. The sub- 

 operculum forms the hindmost part of the giU-covers, and does not 

 cover the exposed portion of the humerus above the root of the pec- 

 toral ; its vertical Avidth is one-half of that of the operculum. 



The origin of the dorsal fin is a little nearer to the end of the 

 snout than to the root of the caudal ; the length of its base is con- 

 siderably more than that of the last ray, and contained once and a 

 third in that of the fourth ray ; the upper margin of the fin is straight. 

 The first ray is nearly half as long as the second, the second and 

 third haK as long as the third and fourth ; the fifth, sixth, and 

 seventh are the longest, the former simple, and the two latter 

 branched ; the last is split to the base, and half as long as the sixth. 

 The distance of the adipose fin from the dorsal is equal to, or rather 

 less than, twice the length of the base of the latter. 



The origin of the anal fin is in the middle between the root of the 

 caudal and that of the outer ventral ray ; the length of its base is 

 less than that of the dorsal, and two-thirds of the length of the fifth 

 ray. The fourth, fifth, and sixth rays are the longest, and form an 

 acute point; the lower margin of the fin is slightly emarginate. 

 The fourth ray is simple, the fifth branched ; the last is split to the 

 base, half as long as the fourth. 



Caudal fin forked, one of the middle rays being two-fifths as long- 

 as the outer ones, the length of which is less than one-fifth of the 

 total. Lobes pointed. 



The base of the pectoral is entirely free, and not overlapped by 

 the gill-cover apparatus ; it is shorter than the head, terminating at 

 a considerable distance from the vertical from the origin of the dorsal ; 

 its length is one-half, or not much more than one-half, of the dis- 

 tance between its root and that of the ventral. 



The ventral is inserted below the tenth and eleventh dorsal rays, 

 its length being four-fifths of that of the pectoral, and two-thirds of 

 that of the head. 



Back bluish black ; sides silvery, with scattered light-salmon- 

 coloured dots ; belly reddish ; fins black, the anal and the paired 

 fins with a reddish tinge, the anal and the ventrals with a narrow 

 whitish margin. 



