S62 LAKE SUPERIOR. 



The opercular apparatus is smaller and more convex than in the 

 preceding species, and all the bones are so, proportionally, I having, 

 however, been careful to take two individuals of the same size for the 

 purpose of comparison. The operculum is as broad as high, though 

 narrower at the upper margin than at the lower, which is oblique ; 

 the posterior margin is almost straight. The suboperculum is more 

 regular, on account of its lower margin being less convex. The 

 interoperculum is less extended on its posterior extremity, which 

 emits no processus along the anterior margin of the operculum. The 

 outer surface is very convex, and almost smooth. The preoperculum 

 is longer and more slender than the interoperculum, and proportion- 

 ally broader than in the preceding species. 



The branchial fissures are large also ; the branchiostegal membrane 

 is strong and thick ; it contains three rays. The dorsal fin is quad- 

 rangular, its posterior margin equals in height two-thirds of its anterior 

 margin, where we observe two or three small rudimentary rays, 

 ■without articulations. Its upper margin is almost straight or subcon- 

 cave. The anal is long, and attains the base of the caudal in the 

 male, whilst it is shorter in the female ; its anterior and posterior 

 margins are parallel on the first two-thirds ; beyond which they 

 approach each other to form a triangle, and to terminate the fin in 

 a more or less obtuse point. The caudal is notched ; the scales 

 advance more on the base of the lower lobe, which predominates 

 slightly over the upper ; but this character is not constant ; I have 

 even observed it only on the single individual which I have had 

 figured ; there is one, sometimes two, rudimentary rays at the ante- 

 rior margin. The ventrals are broad and esrpanded, hke an equi- 

 lateral fan in the male ; while in the female the inner margin is 

 shorter, which changes the aspect of the outer circumference, which 

 is straight and more uniform in the male. Generally, we observe 

 the rudiments of a ray at the anterior margin, which corresponds to 

 the fifth ray of the dorsal, the rudiments excluded. The pectorals 

 are long and of an irregularly elliptical form, or oblong, sometimes 

 pointed at their terminal extremity. The anterior ray is strong and 

 robust ; the fifth is the largest. 



Br. 3; D. 111,11; A. II, 8; C. 5, 1, 8, 8, 1, 5 ; V.I, 10; P. 

 17-18. 



