Fig. 13. — Head of Maine ■whitefish (Coregonus labradoricus). 



RANGELEY LAKES, MAINE: FISHES, ANGLING, AND FISH CULTURE. 52 1 



Whether or not those of the Michigan fish are constant can be told only by an examina- 

 tion of a larger number of specimens. In certain proportional measurements the Umba- 

 gog fish approaches the Maine fish, intergrading or interlinking the Michigan with the 

 Maine form, suggesting that the change to the conditions of environment found in Maine 

 is correspondingly modifying the fish and thus indicating that the differences between 

 the Michigan and Maine fish may be merely ontogenetic. In the dim light of our present 

 knowledge, however, it seems best to continue to regard the native Maine form as a 

 distinct species, although the geo- 

 graphical limits of either form are 

 unknown. 



The most conspicuous and about 

 the only distinct differences shown 

 by the specimens examined are in 

 the shape of the head and form of 

 some of the head bones. In the 

 Umbagog fish, as well as those of the 

 Michigan waters that have been ex- 

 amined, the supraoccipital and parie- 

 tal bones slope from the nape to the 

 f rontals , forming a somewhat concave 

 profile, figure 12. In the Maine fish 

 the profile is always straight and continuous with the line of the nape, figure 13. In 

 the Umbagog fish the opercular bones are proportionally deeper and the supplemen- 

 tary maxillary proportionally longer and narrower than in the Maine fish, and the lower 

 jaw of the Umbagog fish is slightly shorter than in the Maine fish. 



The following comparison of averages of proportional measurements of the Umba- 

 gog, Maine, and Michigan fish, respectively, in many instances shows the previously 

 mentioned intergradation : 



Head of Umbagog fish longer than that of the Maine fish and slightly longer than that of the 

 Michigan form. 



Maxillary, longer than Maine and Michigan, the latter two essentially alike. 

 Mandible, shorter than Maine, about the same as Michigan. 

 Snout, shorter than Maine, intergrading with Michigan. 

 Interorbital, essentially the same in all. 



Eye, about the same as Maine, but somewhat larger than Michigan. 

 Depth, about the same as Maine; less than Michigan. 

 Longest dorsal ray, about the same in all. 

 Longest anal ray, longer than Maine, shorter than Michigan. 

 Pectoral, longer than Maine, shorter than Michigan. 

 Ventral, longer than Maine, shorter than Michigan. 



Longest gill raker compared with eye, longer than Maine, shorter than Michigan. (See Table 

 V, p. 592.) 



The number of gill rakers is somewhat greater than in the Maine fish and some- 

 what greater than in the Michigan form, overlapping both, but the latter more than 

 the former. The increase in the average number of gill rakers does not indicate that 

 the fish is adapting itself to coarser food, as the fact that it takes a small fish bait sug- 

 gests, but rather that its principal subsistence consists of more minute forms. This, 

 if a fact, perhaps will account for it disappearing from the upper lakes and more or 

 less permanently abiding in Umbagog, where the plankton is more abundant. 



