34 MONOGRAPH OF THE FRESH WATER til. 



account of its minuteness. In Acanthocotti, however, it is quite large and easily 

 distinguishable. 



The body is smooth and deprived of scales; it is more or less viscous or slimy, as 

 all fishes generally are. It diminishes gradually in thickness and in height from 

 the head towards the tail. The back is almost straight or slightly arched. The 

 lateral line exhibits in its structure a peculiarity which seems to belong chieflj^, if 

 not exclusively, to all the American species. The subcutaneous cartilages disappear 

 on the last fourth of the line, whence it is continued to the base of the caudal fin 

 by a series of minute pores, subjected to a sudden fall on the peduncle of the tail. 

 This character had already struck Mr. Heckel, who makes of it the distinguishing 

 mark of his C. gracilis, the only American species of which he saw specimens. 



Another character, more or less general, making a distinction between the species 

 of the two hemispheres, is the fact that the rays of the fins have a tendency to be 

 more bifurcated in the species of the old hemisphere than in those of the new. 

 As far as the rays of the j)ectoral fins are concerned, we know only one American 

 species, the G. Wilsonii, in which the upper ones are subdivided. Except in G. 

 BicJiardsonii, where we have noticed some rays of the centre of the second dorsal 

 as showing a slight bifurcation at their summit, we are not aware of any other fin 

 where that character of the bifurcation of the rays exists, except in the rays of the 

 caudal fin generally, although in a less degree than among the European species. 



The first dorsal fin is always lower than the second ; sometimes continuous with 

 the latter by a membrane, sometimes completely separated by a short interval. 

 The length of the pectorals varies according to the species ; their inferior rays are 

 shorter and thicker than the upper ones, and their tips extend beyond the mem- 

 brane which unites them, giving to the lower edge of the fin a scalloped appearance. 



There is, in the structure of the ventral fins, a peculiarity worthy of notice, and 

 which will undoubtedly have a great weight upon the question of the validity of 

 the species in this genus. In some there are four soft and articulated rays, whilst 

 others have but three, all of them possessing the anterior short and spiny ray, 

 closely connected with the first soft one and hidden in the thickness of the skin. 

 Now the European species, mentioned by Mr. Heckel, are all provided with four 

 soft rays to the ventrals, and this also must have struck him as an interesting 

 fact, since the presence of three soft rays constitutes the second character by which 

 he distinguishes his G. gracilis from all others. The study of the American species 

 has taught us that this character had more than a specific value; and, in consult- 

 ing the various documents respecting the history of European species, we became 

 satisfied that the same was the case with regard to these latter. Some may sup- 

 pose this character to be sexual, but we are convinced that it is not the case, 

 having had this question before us from the very commencement of our investiga- 

 tions. Having had series of individuals, young and adult, of most of the species, 

 we always found it constant. Six species have four soft rays : G. cognahis, of 

 Great Bear Lake; G. Bichardsonii, of the northern shore of Lake Superior; G. 

 Alwrdii, of Lake Huron; G. Bairdii, of the north-western tributaries of the Ohio; 

 G. Wilsonii, of the south-eastern tributaries of the same river; and G. meridionalis, 

 from James River (Va.). Now, if we have to deal with a sexual character, we 



