358 LAKE SUPERIOR. 



Catostomus Forsterianus, Agass. 



I possess a complete series of individuals of this species, from the 

 size of eleven inches up to seventeen. My description was made 

 principally from the largest, to bring it nearest to that of O. Mud- 

 sonius ; but I must, at the outset, remark that the characters no- 

 ticed are the same in all. Not possessing a specimen of (7. Hudso- 

 nius, I have referred to the description Dr. Richardson has given in 

 establishing the points of comparison. 



The general form of the body is very regular ; the dorsal and 

 ventral lines circumscribe an elongated oval, approaching to a cylinder 

 towards the head, and to a parallelogram along the tail. The greatest 

 circumference taken on the line of the greatest height, that is to say, 

 before the dorsal, is nine inches and a half. The sides are compressed ; 

 the body passes to the head, or, we might rather say, the head passes 

 to the body, without any enlargement on the nape of the neck. 

 The greatest height of the body does not become double the 

 greatest thickness, this latter being taken at the very origin of the 

 trunk ; thence it diminishes gradually and insensibly towards the 

 caudal region, and the proportion begins to become progressively 

 stronger in favor of the height from the posterior margin of the 

 dorsal. 



The head itself is very smooth, and covered with a thick skin ; it 

 is rather conical than quadrangular, on account of the declivity of 

 the upper surface, which continues from the nape of the neck to the 

 obtuse and rounded snout. It forms about the fifth part of the 

 whole length, or rather less ; its height forms three-quarters of its 

 length, in which the breadth between both eyes is contained twice. 

 The eyes are subcircular, and situated near the upper surface of the 

 head ; the anterior margin of their orbit is at equal distances from 

 the end of the snout and the posterior extremity of the operculum ; 

 in other terms, the diameter of the orbit is contained twice in the 

 space which separates it from the margin of the operculum, and thrice 

 in that which extends between it and the rostrum. The nostrils are 

 large, and at a distance of one-fourth of an inch from the anterior 

 margin of the orbits ; their structure varies little in different species. 



