[cox] FRESH WATER FISHES AND BATRACHIA 147 



could be expected, where it was observed last summer in the Metapedia 

 river and lake, Grand and Little Cascapedia, Nouvelle (New Carlisle) 

 lakes, and in the basin of the Grand Pabos (Lac à Canard and Murphy's 

 Lake.) 



The genus is widely distributed in North America, consisting, 

 however, of only a few closely allied species, whose differentiation is 

 made to rest upon such slight and varying characters as to render the 

 classification a mere recognition of the extremes of varieties, blending 

 with each other through a series of intermediate forms. For the pur- 

 pose of illustrating this point, it is only necessary to compare with one 

 another the three most dominant northern forms, C. plumbeus, Gunther, 

 C. dissimilis, Girard, and C. greeni, Jordan. The first is our alleged 

 eastern form ; the second peculiar to Lake Superior and the northern 

 and northwestern portion of the Mississippi basin ; the last a recently 

 described species from Fort St. James, B.C. (Bull. Nat. Hist. Soc. of 

 B.C., 1893). The element of chief value, indeed of any value, is the 

 scale formula, which is as follows : — 



C. greeni, 10-57-7. 



C. plumheus, 11-65-7 (11-60 to 70-7). 



C. dissimilis, 12-68-8. 



To one who has been afield, examined hundreds of specimens, and 

 noticed the wide range of variation in this respect among stock of the 

 same place or neighbouring places, the founding of species on such 

 small, inconstant, and largely accidental differences must appear as little 

 else than designating the extremes of variation in a given species. The 

 writer has found plumheus to vary from 10-60-7 to 12-70-8, and hence 

 to comprehend within its limits the three above species, at least as far 

 as this feature — the chief one — is concerned. To the relative height, 

 too, of the dorsal and the form of its free margin is attached some sig- 

 nificance in the attempted separation of dissimilis from plumbeus, the 

 former having the margin nearly straight with anterior rays not pro- 

 duced, the latter with the margin concave and rays produced. When 

 somewhat marked, constant, and associated with other contrasts^, the 

 feature would be of some value ; otherwise it should be used with much 

 caution, for it is just in these two respects that fins of the same species 

 are often found to differ. Age, sex, season, and nature of summer and 

 winter habitats are modifying causes. Anadromous tribes and fishes 

 of lacustrine habit, resorting to the upper courses of rivers for breeding 

 purposes, exhibit at different seasons a considerable variation in this 

 respect. Our Atlantic salmon is a good example. Under these circum- 

 stances there is extra wear or abrasion of the anterior rays and external 

 parts, often materially changing the outline. CeratichtJiys exhibits all 



