368 LAKE SUPERIOR. 



constitute by themselves a distinct genus, to wluch my (xohio plum- 

 beus will also belong, as it is not to be separated generically from 

 Leuciscus pulchellus and other American species. 



Leuciscds frontalis, Agass. 



PI. III., fig. 4. 



At first sight this species reminds us of L. cornutus of New Eng- 

 land, to which it bears a close resemblance. Its general form is 

 short and stout. Its sides are much compressed. The back is very 

 convex. The height of the body is proportionally great, and is con- 

 tained only four times in the whole length, from the anterior extremity 

 of the head to the termination of the caudal. It has thus a corpu- 

 lent form, and is even higher than L. cornutus. The tail also 

 loses its dimensions less abruptly. The head itself participates of 

 the abbreviated form of the body, being somewhat less than a quarter 

 of its length. Its upper surface is rounded, very declivous, and de- 

 scends abruptly on the snout, which renders it very obtuse, rounded, 

 and, as it were, prominent. The eyes are large and circular, pro- 

 portionally larger than in L. cornutus, and approach less to the top 

 of the head. They are situated but little nearer to the end of the 

 snout than to the posterior margin of the opercular apparatus. The 

 lower margin of their orbit corresponds to a horizontal line traced 

 along the middle of the face. The nostrils open by a double opening 

 in a circular depression situated before the eyes, and nearer to these 

 latter than to the terminal margin of the head. The anterior 

 opening, which is the smallest and of subcircular form, is bordered 

 behind by a small membrane which applies itself like a cover on the 

 posterior opening, rendering its form crescentic. The mouth is of 

 medium size, but shorter cleft ; its angles attain a vertical line which 

 would descend from the nostrils ; it is terminal and oblique ; the 

 lower jaw is somewhat shorter than the upper. 



The opercular apparatus has nothmg remarkable. The bones 

 which compose it are all hidden beneath a thick skin through which 

 we scarcely distinguish theu' outlines. All are rounded on their 

 outer margin, and give to the extended outline of the whole opercu- 



