38 MONOGRAPH OF THE FRESH WATER III. 



In 1845, Mr. W. 0. Ayres wrote a somewhat extensive Memoir 1 with a view of 

 demonstrating the identity between C. cognattis of Richardson. ('. /-/Wxwu* of llaloV- 

 man, and l'r<m'tca quiescena of Dekay. The individuals under examination, 

 taken as a standard, were all secured in the State of Connecticut, and are indeed 

 identical with the species described by Dr. Dekay. C. viscosua and C. cut/unfit* on 

 the contrary, are two other perfectly distinct species. 



After having referred to one and a single species, all the American Cotti, Mr. 

 Ayres proceeds to establish the identity of this one and unique species, with the 

 European C. gobio. But we would ask, why should it be identical with C. gol/io, 

 rather than with any one of the others found in Europe or Asia? Mr. HeckcTs 

 investigations being not known in this country in 1845, Mr. Ayres was still under 

 the impression that C. gobio was the only species of the genus in the old world ; 

 whence the idea of identifying with it those of North America. 



Without recapitulating here what we have said in the introduction, respecting 

 the European Cotti, we may recall to mind that the ('. <i<>l>in is not yet determined 

 with accuracy, and that under such circumstances the comparisons lose somewhat 

 of their value. Some have taken for terms of comparison the C. <il>i<> of England ; 

 others, that of the Seine ; still others, that of the Rhine, of the Danube, &c. &c., 

 and now, if these are, as we believe, types of several species, which can we call at 

 present C. gobio? Had Mr. Ayres been aware of this state of things, he would 

 have himself admitted, that it was more than premature to bring under this 

 appellation, the American Cotti. 



It is evident that after C. viscosua and C. cognafus are identified with C. <//<" // /'.> 

 it is no longer possible to discern between spci-lfu- <-h<> i-m-f/ /*,- the idea of the genus 

 alone is left to the mind. After this is done, you may read Artedi's description, 

 and nothing will be more natural than to find it agreeing perfectly with all existing 

 Cotti. There is a generic identity and not a specific one. 



Thus, we shall consider C. cot/nnta* and C. viscosiis as two distinct species, as 

 they were previous to 1845. We erase the name of Coitus golno from the catalogue 

 of fishes of the United States, into which it was too hastily introduced, recalling 

 here to mind that wherever a complete study of the species of fish reputed identi- 

 cal in both continents within the limits of the Temperate Zone has been made, the 

 results have been that species difler from one continent to the other. Yet we 

 would not allow any one to conclude them distinct /<//'<///, on this ground. We 

 cannot, on the contrary, too much insist upon the necessity of direct observation- 

 and immediate comparisons. 



In 1850, appeared the descriptions of two new species brought from Lake Supe- 

 rior, by Prof. Agassi/.. 



Our own re-eaivhes have made us acquainted with eight others, liesides a ninth, 

 which constitutes a new genus; so that the whole number of the Cottoid group 

 included in the present work amounts to fifteen. 



There are a lew more species which will be made known to science in the Ichthy- 



1 Boston Journal of Natural Hi-t.try, v., p IP', 



