42 BULLETIN OP THE NATURAL HISTORY SOCIETY. 



men had the scale formula 12-70-9, the snout very short, 

 the head broad and flattish, and the lateral band invisible. 



Being denizens of both fluviatile and lacustrine waters, 

 much variation must be looked for, even in those 

 details of general physiognomy which are regarded as 

 specific of fishes of more uniform habitat and restricted 

 range. Food, temperature, and the character of its 

 general environment must, in time, stamp their influence 

 on the less persistent structural elements of the creature 

 so conditioned, and slowly produce that divergence of 

 type to which the very existence of species is doubtless 

 due. The cyprinids are peculiar among fishes in this re- 

 spect, which renders the family one of the most difiicult 

 to diagnose and classify. Moreover, there is much con- 

 fusion at present in the literature relating to the genus 

 Coueshis, and a more thorough examination of a large 

 amount of material from various sources may perhaps 

 show that many of these apparently aberrant forms may 

 be entitled, if not to specific, at least to sub-specific dis- 

 tinction, 



Couesius prosthemius Cope. 



Though this distinguished herpetologist and natural- 

 ist considered this form a good species, there are many 

 reasons for simply regarding it as a strongly marked 

 variety or perhaps sub-species of C. jylumbeus Agassiz. 

 Even Giinther adjudged it of specific rank {vide VII. p. 

 442) ; but the writer is not aware that he had then seen 

 the last described species. This fish occurs in Loch 

 Lomond, St. John County, where it was identified by 

 the writer in June, 1893. It is very abundant, and 

 would seem to iittain a larger size than in any other re- 

 corded place in America, except perhaps in Lake 

 Superior, some specimens being over six inches long. 

 The following description w^ill sufiice : Body elongate. 



