282 LAKE SUPERIOR. 



their anterior margin, the smallest of the four pairs, have exactly 

 the length of the space contained between them and the anterior 

 extremity of the head. Thej are soft, flabby and rounded. The 

 eyes, proportionally small and subcircular, are at a distance of one 

 inch from the anterior margin of the head. Their diameter is five- 

 sixteenths of an inch. The four barbels of the lower surface of the 

 head are placed upon an arc of a circle within the branches of 

 the jaw. The two internal ones are more distant from each other 

 than the external ones. These latter are one and one-sixteenth 

 inches long, whilst the former are only seven-eighths of an inch. 

 They are soft upon their whole extent, like those of the nostrils, 

 rounded and elongated. 



The opercular apparatus is almost completely hidden under the 

 skin and the muscles ; a slight swelling indicates the inferoposterior 

 margin of the operculum. As for the preoperculum, which forms the 

 anterior outline of the apparatus, we can trace its whole margin, 

 which is arched within, and upon which the branchiostegal mem- 

 brane is fixed. The branchiostegal rays themselves are nine in 

 number ; the first two, the most developed, are of about equal 

 size, and follow the outline of the preoperculum, without being 

 attached there otherwise than by the muscles which move them. 

 All are flattened and concave on their outer surface. The humeral 

 apophysis, which we perceive through the skin, is strong and robust. 

 It extends two-thirds the length of the spine of the pectoral fins ; 

 its outer margin is wrinkled. 



The dorsal fin is composed of a spinous and six soft rays. Its 

 basis measures one and one-eighth inches, the spine is one and 

 one-half inches long ; the rays of the centre, one and five-eighths 

 inches. Hence the fin has a quadrilateral form from its in- 

 sertion to the height of the spinous ray, terminated by an isosce- 

 les triangle. The spinous ray itself is slender, slightly arched ; 

 its posterior margin has neither furrows nor denticulations. At its 

 upper third is implanted a rudiment of a soft ray which takes 

 an oblique direction upwards. The adipose fin is of medium size, 

 thick at its basis, thin upon its circumference, which extends a little 

 beyond the posterior margin of the insertion of the anal. It is seven- 

 eighths of an inch long. The caudal is subtruncate, almost concave. 



