THE WHITEFISHES OF NORTH AMERICA. 311 



Among the collections recently made there are 8 specimens of Argy- 

 rosomus (5 from Lake Michigan and 3 from Lake Superior) which we 

 refer to A. hoyi for the present, though they differ from typical Jioyi 

 in some respects. The most important of these is the number of gill- 

 rakers. In the numerous specimens of hoyi examined the average 

 number; of gillrakers was found to be 39, while the average for the 8 

 specimens here considered is but 31J. If we consider only these aver- 

 ages the difference is great, but the range of variation in each is .so 

 great as to render this contrast less striking. An examination of the 

 table under hoyi shows the range to be from 37 to 42, and the following 

 table shows the range in these 8 specimens to be from 29 to 34. The 

 difference of 3, however, between the minimum for hoyi and the maxi- 

 mum for these peculiar specimens is important, and would, under ordi- 

 nary circumstances, lead us to regard these 8 specimens as belonging 

 to another and apparently undescribed species. 



These specimens also resemble A. prognathus in general appearance, 

 and a comparison with that species is equally interesting. The chief 

 differences from A. prognathus, which can be represented numerically, 

 are the fewer gillrakers, the longer mandible, and shorter maxillary. 

 The average number of gillrakers in A. 'prognathus is, as .shown by our 

 material, about 39. These averages are sufficiently wide apart to jus- 

 tify separating the two forms specifically; and we would not hesitate 

 to do so were it not for the fact that the recognized extremes of varia- 

 tion in this particular in A. prognathus are very great, the minimum 

 number recognized by us in that species being as low as 32 (in speci- 

 mens Nos. 23 and 25). But the other characters shown by these two 

 specimens are not appreciably different from typical prognathus. They 

 have the projecting lower jaw, the long mandible and maxillary, and 

 the general form of muzzle of that species. 



In the 8 specimens under consideration, not only are the gillrakers 

 very few, but the mandible and maxillary are rather shorter, and the 

 general form of the snout is different. The lower jaw projects but 

 slightly or not at all, and the maxillary is narrower. Nos. 108 to 112 

 were obtained in deep water off Sheboygan, Wis., with Hoy's whifefish, 

 from which they were not distinguished by the fishermen, all being 

 known to them as "kieye" or "chub."' While these fish were con- 

 founded with A. hoyi by the fishermen, they appear more different from 

 that species than they do from A. prognathus, the gillrakers in .1. hoyi 

 being even more numerous than in prognathus. Externally they very 

 closely resemble hoyi, while in number of gillrakers they seem more 

 closely related to the longjaw. If further investigation should show 

 these differences to be as great and valuable as they now appear, these 

 specimens should be regarded as a distinct species. For the present, 

 however, we suspend judgment and await additional evidence. 



