FISHES OP LAKE SUPERIOR. 369 



The mouth is placed immediately beneath the extremity of the ros- 

 trum ; it is of medium size, very protractile ; its opening is subcircular, 

 and easily receives the largest finger beyond the first phalanx. Its 

 lips are carunculate ; the upper is thin, and of equal breadth on the 

 whole circumference of the jaw ; it dilates itself from the angle of 

 the mouth, to pass to the thickened and rounded lobes, with fringed 

 circumference of the lower jaw ; these fringes are equally visible 

 on the margin of the upper lip ; the two lobes are united on the 

 symphysis of the jaw, by a narrow cutaneous slip ; the caruncles 

 which cover their surface are scarcely more marked than those of 

 the upper lip. On the head we remark several rows of pores similar 

 to those of 0. Rudsonius and other species. These rows are per- 

 fectly distinct in individuals preserved in alcohol. One of them is the 

 continuation of the lateral hne of the body ; it passes along the upper 

 margin of the operculum, descends beneath the orbit, and terminates 

 on the end of the snout, describing some undulations on its pas- 

 sage. The second row begins at the nostrils, and terminates on the 

 occiput, a little before the union of the head with the body, on which 

 point of union we observe a third single row, united transversely 

 by its two extremities to the first double row. Finally, a fourth row 

 is situated upon the face, and follows the outer margin of the pre- 

 operculum. 



The opercular apparatus differs from that of O. Hudsonius, as 

 described by Dr. Richardson, in two of its bones, the preoperculum 

 and the interoperculum. This latter, in the species which is here 

 referred to, has exactly the length of the suboperculum, though it is 

 more robust and of more irregular form. It has a median carina on 

 its anterior angle, whose extremity reaches that of the preoperculum 

 in contact with the lower maxillary ; the posterior part, contiguous to 

 the operculum and suboperculum, is triangular, and rises to one-third 

 of the height of the anterior margin of the operculum. The pre- 

 operculum is more slender, more elongated, and narrower than the 

 interoperculum ; its form is that of a very opened crescent. 



The branchial fissures are very large, and somewhat approximated 

 on the isthmus, where the membrane passes to the integuments of 

 the abdomen, appearing somewhat like a transverse furrow. 



The intestinal canal measures twice the length of the body. The 



