FISHES OF LAKE SUPERIOR. 335 



The opercular apparatus differs considerably from that of S. na- 

 mai/cush ; in the fresh condition it is covered with a thick skin 

 which hides the outlines of its bones. The preoperculum is long, of 

 the form of a very opened crescent, placed almost vertically ; its 

 posterior margin is attenuate and entire ; its lower branch is more 

 extended than the upper. The operculum of greater height than 

 breadth, is large and notched at the summit, but without prominent 

 processes on the rest of its circumference, which is irregularly circu- 

 lar ; the posterior middle part, however, has a tendency to make a 

 projection ; the lower margin is denticulate. The suboperculum is 

 one-third smaller than the operculum, irregularly elliptical, pointed 

 at the summit, with an ascending ridge in the form of a fish-hook 

 at its articulation. Finally, the iuteroperculum has the form of a 

 long square, curved on the posterior side ; its height is contained 

 twice in its length. 



The branchiostegal rays are thirteen in number, their length 

 diminishing very gradually from the opercular apparatus beneath the 

 throat, where the last is only one-third smaller than the first. This 

 latter can scarcely be distinguished from the interoperculum, so thin 

 and dilated is it ; it is only a little more narrow, and we remark 

 that it has a tendency to bend itself. The curve is stronger on the 

 four following, which are still very dilated compared to the eight 

 remaining, which are not larger than ordinary rays, and flattened, 

 with a more marked elbow on their extremity of insertion, which, 

 moreover, is curved inwards. 



The fins on the whole are strong and proportioned to the body 

 which they have to support and to move. The dorsal, which is larger 

 than in the 8. namaycush, is higher than it is long, and occupies 

 exactly the middle of the back ; its margins are straight. The 

 adipose, opposite to the posterior margin of the anal, is narrow, lan- 

 ceolate, with an elliptical summit turned backwards. The caudal is 

 ample and slightly furcate, much less furcated than in S. namaycush. 

 The anal is as high as the dorsal, but not as long as this latter, 

 though its rays are more numerous ; they are there very dense, and 

 the three first are shorter than the fourth ; its terminal margin is 

 straight. The ventrals are inserted beneath the dorsal, vertically, 

 under the seventh ray ; they do not reach the anus behind ; their 



