462 Bulletin 47, United States National Museum. 



and slender. Air bladder very large. Vertebrae 56 to 60. Stomach horse- 

 shoe-shaped, with many (about 100) pyloric coeca. Ova small. Species 

 about 15, inhabiting the clear lakes of northern Europe, Asia, 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 con- 

 siderable depths. The number of distinct species of Coregonus has been 

 overestimated by many writers. The geographical range and range of 

 variation of each one are much wider than has hitherto been generally 

 supposed.* The species are highly valued for food, the flesh being gen- 

 erally pale and of fine flavor. The coloration is very uniform ; bluish 

 olivaceous above ; the sides and below silvery. ( Coregonus, a name used by 

 Artedi for t'he European lavaret, or whitefish, Coregonus lavaretus, from 

 Koprj, the pupil of the eye ; yuvia, angle; " quia pupilla anteriore parte in 

 angulum- acutum procurrit." Artedi.) 



PEOSOPIUM (irpoo-taniov, a mask, from the large preorbitals) : 



a. Gill rakers Bhort, thickish, about 12 to 16 in number on the lower limb of the arch; max- 

 illary short, broad, not reaching eye, the supplemental bone mostly narrow and 

 Bharply elliptical; mouth small. 

 b. Mouth comparatively large, the maxillary about 4 in head; gill rakers very short and 



thick, 10 -f 16; body oblong, the back not elevated. 



c. Scales large, 60 to 63 in lateral line; snout blunt and decurved. COULTERII, 7^5. 

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



(7. Supplemental bone of maxillary rather narrow; scales 83 to 90. 



e. Head moderate, blunt anteriorly, 4% to 5 in body; tip of snout below 

 level of eye; gill rakers short, 9 + 15; lower fins pale. 



WILLIAMSONI, 756. 



ee. Head very short, blunt, 5% in body; gill rakers short and slender, about 

 7 + 14; fins all blackish. KENNICOTTI, 757. 



<M. Supplemental bone of maxillary very broad, semicircular; scales 72 to 80. 



RICHARDSON1I, 758. 



bb. Mouth small, the maxillary 5 to 5% in head; gill rakers shorter and thicker, about 

 7 + 10, about 5 in eye, fewer than in C. williamsoni. Body elongate, the back not 

 elevated nor much compressed. QUADRILATERALIS, 759. 



COREGONUS: 



aa. Gill rakers numerous, long and slender, 17 to 20 on the lower limb of the arch; preorbi- 

 tal long and narrow; maxillary rather long, more than % head, the supplemental 

 bone ovate. 

 /. Tongue toothless or nearly so; back ele.vated; head very low and short, especially in 



old examples. 



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



nearly twice as long as deep. CLUPEIFORMIS, 760. 



gg. Back elevated and much compressed; supplemental bone of maxillary more than 



% as deep as long; gill rakers about 26. NELSONII, 761. 



ff. Tongue with 3 series of small teeth; body elongate, compressed; lower jaw slightly 



included. 

 h. Gill rakers short and few, about 10 + 15, the longest about 2 in eye. 



LABRADORICUS, 762. 



Subgenus P OSOPIUM, Milner. 

 755. COREGONUS COULTERII, Eigenmann & Eigenmann. 



Head 4$ to 5 ; depth 4i to 5i ; eye 4 ; snout 4. D. 10 or 11 ; A. 10 or 11 ; 

 scales 8-60 to 63-6. Form rather heavy, little elevated; the snout broad, 



*For a useful analytical key to the species of Coregonus, see Bean, in Trans. Amer. Fish 

 Cultural Ass'n, 13th annual meeting, 1884, 33. 



