The Whitefishes 



deeply forked; pseudobranchiae large; gillrakers varying from short 

 and thickish to long and slender; air-bladder very large; eggs 

 small. 



Species about i8, inhabiting clear lakes of northern Asia, 

 Europe and America, in Arctic regions descending to the sea. 

 Most of them spawn in late fall or winter near the shore, at 

 other seasons often frequenting considerable depths. All the species 

 are highly valued for food, the flesh being generally pale and of 

 excellent flavour. 



The colouration is very uniform; bluish-olivaceous above, 

 silvery on the sides and below. 



a. Gillrakers short, thickish, about 12 to 16 in number on the 



lower limb of the arch; maxillary short, broad, not reach- 

 ing the eye, the supplemental bone mostly narrow and 

 sharply elliptical. 



b. Mouth comparatively large, the maxillary about 4 in head; 



gillrakers very short and thick, 10 to 16; body oblong, the 

 back not elevated. 



c. Scales large, 60 to 6} in lateral line; coulterii, 119 



cc. Scales small, 72 to 90 in lateral line. 



d. Supplemental bone of maxillary rather narrow; scales 85 1090. 



e. Head moderate, blunt, \\ to 3 in body; gillrakers short, 



9+ 1 5 ; lower fins pale; . . . . , williamsoni, 1 19 



ee. Head very short and blunt, 5| in body; gillrakers short and 



slender, about 7 + 14; fins all blackish; heiinicotti, 121 



dd. Supplemental bone of maxillary very broad, semi-circular; 



scales 72 to 80; richardsoni, 121 



bb. Mouth small, the maxillary 5 to s|- in head; gillrakers shorter 



and thicker, about 7+10, about 5 in eye; body elongate, 



the back not elevated, not much compressed; 



quadrilateral is, 1 22 

 aa. Gillrakers numerous, long and slender, 17 to 20 on the lower 



limb of the arch; maxillary long, less than 4 in head, the 



supplemental bone ovate. 

 /. Tongue toothless or nearly so; back elevated; head very low 



and short, especially in old individuals. 

 g. Back elevated, not greatly compressed; supplemental bone of 



maxillary nearly twice as long as deep; clitpeiformiis, 123 



gg. Back elevated and much compressed; supplemental bone of 



maxillary more than | as deep as long; nelsonii, 130 



ff. Tongue with 3 series of small teeth; body elongate, com- 

 pressed ; labradoricus, 1 2} 



118 



