FISHES OF LAKE SUPERIOR. 273 



between the mouth and the termination of the snout, a little nearer 

 however to the mouth. On this face, though generally flattened, we 

 may observe a median longitudinal swelling, having on each side a 

 depression with widened margins. This skin is bare, although cov- 

 ered upon its surface with a net of irregular meshes in which we 

 observe small holes which secrete the mucosity, as in A. Icevis. 



The escutcheons of the dorsal row are twelve in number, well de- 

 veloped, and a rudimentary thirteenth applied to the anterior margin 

 of the dorsal. They are so near to one another that some are even 

 slightly imbricated. Their general form is heart-shaped, broader 

 than long, the two sides limited by a regular denticulated curved 

 line, rising abruptly so as to form a very sharp median carina, 

 terminated at the two posterior thirds in a hook, whose point is 

 turned backwards. Their surface is covered with radiating lines, 

 owing to the linear arrangement of their tubercles, which are exces- 

 sively small, and acute. On the space between the posterior mar- 

 gin of the dorsal and the origin of the caudal we observe three 

 small plates. The largest is situated on the side of the dorsal, the 

 two smaller follow immediately and are arranged in pairs. Their 

 surface is equally covered with small acute tubercles, but the cen 

 tre is scarcely indicated by a larger tubercle, whence the others 

 radiate. (See pi. 5, fig. 3.) 



The lateral escutcheons are from thirty-two to thirty-three in num- 

 ber, of irregular oblong form, with the two sides retracted. The 

 anterior margin is concave, the posterior convex, slightly notched 

 in the middle. The median carina is but slightly prominent, the 

 sides of course but little inclined ; the hook which rises above it is 

 slightly curved backwards ; sometimes it is bifurcated at its point. 

 The surface, as usual, is covered with small granules in radiating 

 rows. Their position in relation to the body is oblique from before 

 backwards. They are less serrated than those of the back, and di- 

 minish gradually as they approach the tail. 



The escutcheons of the abdominal region, from ^even to eight in 

 number, extending over the spaee contained between the posterior 

 margin of the pectoral and the anterior margin of the ventral 

 fins, resemble much in their general outlines those of the back. 

 Their form is perhaps more rounded, though they do not form a 



