318 LAKE SUPERIOR. 



omy. In the present instance, we have had no occasion to hesitate. 

 Having seen by turns the general form, the outlines of the fins, the 

 outer details of the head, and the color, sometimes varying in the 

 same species to a great extent, and at others preserving a monot- 

 onous uniformity, we have taken for our guide the structure of the 

 mouth, and particularly that of the palatal bones and of the vomer, 

 and we may say, that whenever we have had series of specimens at 

 our disposal, the general traits of the species have not varied sensi- 

 bly. We have relied still more confidently on this method, when, 

 after comparing the buccal apparatus, we have seen the extreme 

 variations stop in these limits. 



What strikes us, especially in the species here referred to, is the 

 general smallness of the rows of palatal and vomeric teeth. None 

 make a strong projection above the others. The surface of the 

 palatals has a very uniform appearance, and it is only when we ex- 

 amine them closely, that we perceive that the teeth of the inner row 

 alone exceed those of the body of the bone in size by about one-third, 

 though remaining equal among themselves. The palatal bones 

 themselves are slightly bent, with the convexity turned inwards. 

 Their greatest length is one and a half inches, their greatest breadth 

 one-third of an inch, which maintains itself on the anterior two- 

 thirds, diminishing sensibly on the posterior third, the extremity of 

 which terminates in an oblique line, extending from the front back- 

 wards. The anterior margin is oblique from behind forwards, as in 

 most species, owing to the curve of the snout. The vomer, includ- 

 ing its dilatation and the narrow band, is one and nine-sixteenths 

 inches long. The dilatation is of a triangular form, rounded at the 

 anterior margin, and slightly concave on its sides ; its centre is 

 depressed, concave. A certain number of teeth, larger than those 

 of the centre, occupy its circumference. The narrow band of teeth 

 upon the vomer is lanceolate, and terminates in an acute point a little 

 beyond the extremity of the palatals. We barely observe a con- 

 traction at the place where it enlarges at its anterior part. In the 

 centre it is one-eighth of an inch broad. The teeth which cover 

 its surface are very small. The intermaxillaries do not measure 

 five-eighths of an inch ; they have a single row of teeth as small as 

 those of the vomeric band. The same is the case with the teeth of the 



