FISHES OF LAKE SUPERIOR. 301 



height forms a little more than the half. Besides being very 

 depressed and flattened, the head further presents a slight depression 

 on -the occiput. The mouth is large, its breadth measures nearly six- 

 eighths of an inch. The jaws are of equal length, bordered with 

 excessively fine teeth, with very hooked points. The upper jaw is 

 shghtly protractile. The hps are considerably developed and form 

 a very marked rounded process, on both sides of the lower jaw. 

 The eyes of a circular form, with a diameter which exceeds a quar- 

 ter of an inch, are placed at a distance of three-eighths of an inch 

 from the end of the snout. The nostrils occupy about the middle of 

 this space. The spine of the preoperculum scarcely forms a pro- 

 jection through the skin ; it is strongly bent upwards and back- 

 wards. The upper and hinder angles of the operculum terminate 

 in a small process, flat and sharp, which remains hidden in the 

 thickness of the membrane which encircles the free margin of this 

 bone. The branchiostegal rays, six in number, on each side, are 

 slender and cylindrical. The isthmus between the horns of the 

 hyoid bone measures half an inch. 



The form of the body is regular, gradually decreasing towards the 

 tail. The line of the back is raised ; that of the belly is about 

 straight, forming the continuation to the flattening of the lower sur- 

 face of the head. The greatest height corresponds to the anterior 

 margin of the first dorsal fin ; it measures three-fourths of an 

 inch, whilst the transversal diameter of that same region measures 

 nearly six-eighths of an inch. Above the tail the height is but five- 

 sixteenths of an inch, and the thickness one-eighth. The tail itself is 

 slightly dilated and rounded at the insertion of the caudal. 



The fins upon the whole are much developed. The first dorsal 

 has a basis of six-eighths of an inch, and is five-sixteenths of an inch 

 high, and is situated at one and three-eighth inches from the end of 

 the snout. Its upper margin is rounded, the rays of the centre 

 being the longest ; they are eight in number and undivided. The 

 second dorsal, twice as long as the first, and one third higher, is 

 composed of eighteen rays, the longest occupying the centre of the 

 fin ; a single one of them is dichotomized at its upper end. The 

 caudal, about six-eighths of an inch long, is truncated behind. Its 

 upper and lower margins are shghtly rounded. Thirteen rays may 



