FISHES OF LAKE SUPERIOR. 271 



A character common to all fins is to have the outer margin sen- 

 sibly thicker than the inner, which becomes thin and membranous. 

 It is also in this outer margin that are found the largest rays, 

 arched from within outwards, undivided in the greatest part of their 

 extent, thus giving them a peculiar aspect. Small tubercles are 

 observed in the outer third of the rays where they are most 

 dichotomized. 



The color is of an uniform blackish brown, which extends to the 

 fins ; it is a little less intense on the head, on the lower half of the 

 sides below the middle hne it has a yellowish reflection. A pale white 

 exists over the lower part of the head and the abdomen, as far as 

 the under surface of the tail. 



This species resembles the A. riibicnndus of Lesueur, who describes 

 two varieties of it, one found with the true ruhicundus in Lakes 

 Erie and Ontario ; the other inhabiting the River Ohio. The 

 descriptions which he has given of them do not enable us to recog- 

 nize our species in either of these varieties. 



ACIPENSER CARBONARIUS, AgaSS. 



The general form of this species is rather thick and short than 

 slender. The back is proportionally very elevated and very convex 

 from the occiput to the anterior margin of the dorsal fin, from whence 

 the body begins to grow considerably slender towards the tail, which 

 last rises obliquely in order to form the higher arch of the caudal 

 fin. (Plate 5, fig. 1.) 



The total length is one foot two inches and a half. The head is 

 contained three times and a half in this length. The face, from the 

 anterior margin of the branchial cavity to the extremity of the snout, 

 equals the fourth part of the length of the trunk. The snout, from 

 the orifices of the nostrils is contained seven times in this length. 



The head itself is depressed, flattened, uniformly inclined from 

 the occiput beyond the nostrils, where the snout rises considerably, 

 growing thinner on its margins, which circumstance gives it a convex 

 form. Seen from above, its shape is that of an elongated triangle. 

 The upper surface is quite uniform, having only one slight depression 

 on the middle line, bordered by two small carinse of the frontal and 



