FISHES OF LAKE SUPERIOR. 309 



other, at the extremities of a small furrow, arched outwards. The 

 posterior is the smallest, and occupies the upper and anterior margin 

 of the eje ; the second is placed nearer to the snout than to the eye 

 itself. 



The scales which cover the opercular apparatus are excessively 

 thin, and allow the form and outlines of the different bones to be 

 distinottly seen, the surface of which presents the same silver-colored 

 reflection as the bare space before the pectorals, which extends also 

 beneath the head. The ascending branch of the preoperculum is 

 almost straight at its hinder margin, which is thinned ; the lower 

 angle is rounded. The operculum has the form of a slightly obtuse 

 triangle ; the upper angle is armed with a point ; the margin 

 forming the hypothenuse is shghtly concave or undulated. The 

 suboperculum is proportionally large ; a membranous expansion, in 

 which the point of the operculum loses itself, terminates its upper 

 extremity ; its lower extremity extends before the operculum in the 

 form of a small hook ; the bone itself, like the operculum, is rounded 

 in the form of a stretched and undulated circle, on its circumference. 

 The interoperculum is very small. The cheeks make no projection. 

 The branchiostegal rays, six in number, are bent and flattened. 

 The anus is nearer to the tail than to the head. The lateral hne is 

 direct from the centre of the caudal to the head ; beyond the anal 

 it approaches nearer the back than the belly. The scales are of 

 middle size ; the denticulations of their posterior margin are only 

 visible with the magnifjdng glass. 



Both dorsal fins are distinct and separated from each other. The 

 first begins at three-fourths of an inch from the end of the snout ; its 

 insertion is equal to this distance ; its greatest height, which is at the 

 anterior thirjd, is about one-fourth of an inch, and diminishes gradually 

 towards its posterior margin. The second dorsal is higher than the 

 first, and has a basis of less than half an inch ; it is composed of 

 fifteen bifurcated rays ; its anterior and posterior margins are equi- 

 lateral ; its upper margin slopes from before backwards, its greatest 

 height being at the anterior margin. The caudal has seventeen well 

 developed rays — that is to say — articulated and bifurcated; and 

 eight or nine undivided rudiments on each of its sides ; its pos- 

 terior margin forms a slight crescent ; its upper and lower margins 



