PISHES OF LAKE SUPERIOR. 



height of the trunk corresponds to a vertical line along the middle of 

 the space between the pectorals and the ventrals ; it is contained 

 about three times in the length, exclusive of the caudal. The 

 thickness at the middle of the trunk corresponds to the height as one 

 to two ; it is somewhat less anteriorly, and diminishes gradually 

 towards the caudal region. The head is proportionally small, com- 

 pressed laterally, pointed. Its upper surface slopes as much as the 

 lower rises, so that in adult individuals it appears disproportioned to 

 the development of the trunk, of which it forms only a very small pro- 

 portion. Its length, however, is one-fifth of the whole length, the 

 caudal included. The middle surface of the skull on the suture of 

 the frontals, is slightly conical, and causes the two halves of the skull 

 to appear inclined towards the eyes. These latter are large and 

 subcircular ; the hinder margin of their orbit is at an equal distance 

 between the end of the snout and the free margin of the operculum. 

 The suborbital bones cover the whole space between the orbit and 

 the upper region of the operculum, but leave bare the lower half of 

 the cheeks ; they form a continuous series below the eyes as far as 

 the snout, where this latter elongates itself over the labials, which it 

 receives beneath its lower margin. The nostrils are somewhat 

 nearer to the orbit than to the extremity of the snout. This latter is 

 cut obliquely, and slopes over the lower jaw, which shuts within the 

 intermaxillaries. The mouth is moderate. The intermaxillaries are 

 small, and occupy only the extremity of the rostrum ; they have a 

 row of very small teeth, flexible like bristles. The labials are very 

 short, thin, elongated, and attain the anterior margin of the orbit ; 

 they have on their termination a small shield, which is bony, pearl- 

 hke and included in the skin. The lower jaw seems to be unprovided 

 with teeth, at least we cannot observe any either with the magnifying 

 glass or with the touch. The branches of the lower maxillaries dilate 

 in the form of a very thin blade, which in the state of rest shuts 

 itself up under the suborbital bones. At the anterior margin of this 

 blade we remark a cutaneous expansion, a kind of lip, which is at. 

 tached to the posterior and terminal margin of the labials, and forms 

 thus the angle of the mouth. The tongue is short and broad, free 

 only on its anterior and lateral outline ; its surface, though seeming 

 to be smooth, has some irregular rows of small asperities, which are 



