30 SALMONID^. 



mandible has a slight hook, but the jaws can be brought into perfect 

 contact ; the maxillary bone is longer than the snout by one-half the 

 diameter of the eye : it is rather broad, two -thirds of the width of 

 the orbit, and extends considerably beyond the vertical from the 

 posterior margin of the orbit. The intermaxillary and mandibular 

 teeth are larger than those of the maxillary and palatine bones. 

 The body of the vomer has lost aU its teeth ; and only three remain, 

 forming the transverse series across the posterior part of the head of 

 this bone. 



The distance of the nostrils from the orbit is equal to two-thirds 

 of the diameter of the latter. 



The interorbital space is very convex, the eye being situated 

 below the upper profile of the head ; the width of this space is equal 

 to the length of the snout. Operculum and suboperculum are very 

 thin, and concentrically striated, the striae running parallel to the 

 outer margin. 



The posterior margin of the praeoperculum is subvertical, slightly 

 rounded, the lower limb being distinctly horizontal ; the posterior 

 margin of the operculum is almost straight, oblique, forming a right 

 angle with the inferior limb ; the suboperculum is less than thrice 

 as long as broad. The distance from the angle of the operculum to 

 the lower anterior end of the suboperculum is three-quarters of that 

 from the upper end of the giU-opening to the first-named point. 



The distance of the occiput from the origin of the dorsal fin, if 

 measured back from behind that fin, reaches almost two-thirds of 

 the space between the adipose and the root of the caudal fin. The 

 dorsal fin is as long as high, and consists of thirteen rays, the first 

 three being rudimentary and covered by the skin, the fourth and 

 fifth simple, the latter being as long as the following one, which is 

 branched and the longest in the fin ; the final ray is cleft throughout. 



The anal fin is higher than long, and possesses eleven rays, of 

 which the first and second are rudimentaiy and covered by the skin, 

 the third simple, the fourth branched and the longest, and the last 

 ray cleft to its root. 



Pectoral nearly as long as the postorbital portion of the head, 

 reaching nearly two-fifths of the distance of its root from that of the 

 ventral: ventral shorter, very shghtly exceeding one-half of the 

 distance of its root from the vent ; its outermost ray is vertically 

 opposite the ninth of the dorsal. Posterior margin of the caudal fin 

 scarcely emarginate. 



There are 117 transverse series of scales, counted immediately 

 above the lateral line ; the scries descending obliquely backwards 

 from the origin of the dorsal fin to that line has twentj'-six scales ; 

 that forwards from the hinder end of the adipose has fifteen scales. 

 There are twenty-two longitudinal series between the lateral line 

 and the root- of the ventral. The scales are very thin, without a 

 trace of keel, and with the hinder margin rounded. 



Bright silvery, greenish on the back, and with a shght i)urple shade 

 on the side ; the upper half of the body is densely covered with irre- 



