360 LAKE SUPERIOR. 



lower pharyngeals form a complete ring around the oesophagus. 

 Each bone, taken by itself, resembles in its form a sickle ; that is to 

 say, a crescent with a stalk. With this short, robust and flattened 

 stalk the two bones unite, by means of a muscular bridge, which 

 modify constantly the separation of which they are capable. The 

 crescent presents two distinct sides ; one, the inner, is compact, 

 rounded and smooth, and is only the continuation of the stalk; 

 the other, or outer, is widened, embracing only the circumference of 

 the crescent ; it is composed of vertical laminae, of which the teeth 

 are the continuation, with the exception of two lower ones, which 

 are implanted on the very body of the bone. There are about thirty 

 teeth ; the lower are much developed, strong, and compressed later- 

 ally, surmounted by a crown which slopes over their inner side. 

 From the middle of the crescent the teeth diminish abruptly towards 

 its summit, and are reduced to feeble laminae, which are lost in the 

 body of the bone, which is also subject to a gradual diminution from 

 the stalk to its upper angle. 



The air bladder is composed of two compartments ; the anterior 13 

 pear-shaped, and not quite half the length of the posterior, whose 

 form is cylindrical. 



The color of this fish is bluish gray on the back, the head and the 

 sides ; upon the sides an orange-colored red tint, with a very fine 

 reflection, combines itself with the main color ; the belly and the 

 lower side of the head are whitish. The pectoral and ventral fina 

 are gray, on an orange-colored ground ; the caudal has the tint of 

 the back, as also the dorsal ; the anal is sometimes whitish, like the 

 belly, sometimes gray like the ventrals. 



This species is very common along the northern shores of Lake 

 Superior. 



CATOSTOMUS AURORA, Agass. 

 PI. II., fig. 3 and 4. 



CATOSTOMUS FORSTERIANUS Richards. Frankl. Journ. 1823, p. 720 ; 



Fn. Bor. Amer. III., 1836, 116. Ouv. et Vol., Hist. Nat. Poiss. 



1844, 463. Storer Synops. 1846, p. 167. 

 MITHOMAPETH Pen. Arct. Zool. Introd. ccxcix. 



