III. COTTOIDS OP NORTH AMERICA. 41 



least, as those of the latter can be deduced from the description of Sir John Richard- 

 son, are as follow : 1st. A more backwards position of the vent. 2d. The lateral 

 line which does not reach the caudal fin. 3d. The more advanced position of the 

 anal relatively to the second dorsal ; and, 4th, the shorter pectorals compared to 

 the head. 



This species inhabits the northern shore of Lake Superior, where specimens 

 have been collected by Dr. C. T. Jackson and Professor Agassiz, and are now pre- 

 served at Cambridge (Mass.). A small individual of the same species may also 

 be seen at the Smithsonian Institution. 



II. COTTIJS COGWTATIJS, Rich. 



Syn. Cotlns cognatus, Rich. Faun. Bor. Amer. III. 1836, p. 40. — Heck. Ann. Wien. Mus. II. 1837, 

 p. 149. — GiRARD, Proc. Amer. Assoc. Ady. Sc. II. 1850, p. 410; and, Proc. Bost. Soc. Nat. Hist. 

 III. 1850, p. 189. 



This species we only know by the description of Sir John Richardson. This 

 author compares it carefully with C. gobio of England, which we are told it 

 resembles in nuinerous points. But this comparison will be valuable only after 

 the C. gobio of all regions shall have been submitted to a severe criticism, and after 

 we shall be satisfied of the identity or the. difference of specimens collected in all 

 the countries in Europe where that fish has been noticed. We have already 

 mentioned the important fiict observed by Mr. Heckel, that the C. gobio from 

 Scandinavia belongs to a distinct species. 



The C. cognatus appears to have nearly the same dimensions as the C. gobio of 

 England; the shape and size of the head are similar, but the mouth is larger. 

 The head forms one-third of the length, the caudal fin excluded ; its width is equal 

 to its length ; its height is two-thirds of its breadth. The jaws are of equal length. 

 The premaxillaries, the dentaries, and the vomer, are armed with short, velvet-like 

 teeth. The tongue is smooth, broad, and short. The spine on the preojoercular is 

 small, curved upwards, and hidden under the skin. The branchiostegal rays are 

 slender and cylindrical, as in C. Richardsonii, whilst they are stout and flattened 

 in the C. gobio of England. The isthmus measures half an inch. 



The greatest depth of the body, taken at the origin of the first dorsal, corresponds 

 nearly to the transverse diameter of the same region, whilst towards the insertion 

 of the caudal, the thickness of the body is reduced to the half of its depth. The 

 posterior part of the body is rather acute than rounded. The vent is a little 

 nearer the end of the snout than the insertion of the caudal. The lateral line runs 

 parallel with the back, to which it is nearer than to the belly. 



The origin of the first dorsal takes place a little behind that of the ventrals, at 

 the same distance from the end of the snout as in C. gobio of England; but it 

 extends more backwards, having two rays more,^ the lai'gest of which measure 



' Cuvier gives from six to nine rays to the first dorsal of 6'. (johio; Sir John Richardson informs us that, 

 as far as his observations go, he constantly found six spiny rays to the first dorsal, and sixteen articulated, 

 6 



