SALMONOIDE^. 199 



Head narrow below, with a moderately wide frontal bone, and forming one-fifth of the length, 

 excluding the caudal. The upper surface of the head is smooth and even, in the recent fish, 

 but in drying, the straight, lateral, tubular ridges become visible, traversing a depression over 

 each orbit : the saggital crest is scarcely perceptible, even in the naked skull, and it is cut 

 short anteriorly by a groove which is widest at its termination between the nostrils. The eyes 

 are large, and situated a little more than a diameter of the orbit from the tip of the snout, and 

 near thrice as far from the edge of the gill-plate. The infra-orbitar bones cover more than 

 two-thirds of the cheek : they are traversed by a tubular ridge with short lateral branches. 

 The nostrils are placed midway between the tip of the snout and the orbit. The snout is 

 blunt when seen in front, but its profile is more acute : it projects a little beyond the shut 

 mouth, but when the jaws are separated the intermaxillaries descend from it perpendicularly, 

 the tip of the lower jaw being then in the same line also. The mouth has a small orifice, and 

 w r hen shut its angles are depressed. The intermaxillaries are higher than they are long, or 

 they measure more vertically than they do transversely, so that the orifice of the mouth is 

 farther beneath the snout than in the succeeding species. The labials thin, broad and pyri- 

 form, are articulated by their narrow end to the palatine-bones, in contact with the ball and 

 socket joint of the intermaxillaries : the posterior piece, or appophysis, is as broad as the 

 anterior one and about two-thirds as long. The limb of the under jaw expands into a thin 

 plate, which glides under the anterior sub-orbital when the mouth closes. 



Teeth. — The jaws and tongue are furnished with a few teeth, which are too minute to be 

 readily seen by the naked eye, and too slender to be very perceptible to the finger. The 

 palate and vomer are quite smooth. 



Gill-covers. — The preoperculum is sharply curved and rather broad, its width in the 

 middle equalling the height of the suboperculum. A tubular ridge runs along the anterior 

 edge of its upper limb, and separates on the lower one into four diverging branches. The 

 other bones of the gill-cover are thin and smooth. The operculum measures one-third more 

 vertically than it does horizontally ; while, on the contrary, the suboperculum is twice as long 

 as it is high. The interoperculum is triangular. The gill-membrane is rendered thick by the 

 quantity of muscle and a shining membrane which line its eight thin, flat, curved rays. The 

 branchial arches have each a single row of erect, subulate rakers, a quarter of an inch 

 long, and rough on their inner surfaces. The pharyngeal bones are inconspicuous and 

 toothless. 



Scales rather smaller on the fore part of the belly and back than elsewhere : they are 

 irregularly orbicular on the sides, and about half an inch in diameter. They have a bright 

 pearly lustre, and are thin and very deciduous. The lateral line contains 80 scales, including 

 those on the base of the caudal, and there are 24 in a vertical line before the dorsal, of which 

 10 are above the lateral line, and as many between it and the upper ray of the ventrals. The 

 scales on the lateral line are somewhat smaller, and differ a little in form from the adjoining 

 rows. Lateral line slightly arched in its course along the body, but after passing the anus 

 running horizontally through the tail. 



Colour, in the shade, bluish-grey on the back, lighter on the sides, and white on the belly.. 



