PILOT FISH. 877 



d. Anal fin elongate of 14 to 17 rays. . . . Oncorhykchus. 50. 

 dd. Anal fin short, of 9-11 developed rays. 

 . e. Vomer flat, its toothed surface plain; teeth on the shatt of the vomer in 



alternating rows or one zigzag row, those on the shaft placed directly 

 on the snrtace of the bone, Hot on a free crest (posterior vomerine teeth 

 sometimes deciduons) ; species black-spotted. . . Salmo. 51. 

 ee. Vomer boat-shaped, the shaft strongly depressed ; scales very small, aboat 

 200 in the coarse of the lateral line; species not anadromoas. 

 /. Shaft of vomer with a raised crest, bearing strong teeth, the crest pos- 

 teriorly free; a bai d of stout, recurved teeth on the h>oid bone; 



species gray-spotted Cbistivombr. 52. 



Jf. Shaft of vomer without raised crest, entirely toothless ; species crim- 

 son spotted, the lower fins with marginal bands of black aiid plain. 



SALVKLINnS. 53. . 



Gbnus 49. COREGONUS. Linnaeus. 



Coregonus, Linnaeus, Sytrma Natnrse, 1758 (artedi). 



Argyrosomus, Agassiz, Lake Superior, 1850 {artedi). 



Prosopium, Milner, Mss , Jordan, Man. Vert., 2d Ed., 1878 (quadrilateralia). 



Alloaomus, Jordan, Man. Vert., 2d Ed., 1878 (tullibee). 



Type, Salme ( Coregonus) lavaretue, L. 



Etymology, korre, the temples ; gonoa, angle. 



Body oblong or elongate, compressed ; head more or less conic, compressed, the form 

 of the snout varying considerably; montti small, the maxillary short, not extending 

 beyond the orbit, with a well developed supplemental bone ; teeth extremely minute, 

 if present ; scales rather large, cycloid, about 80 in the course of the lateral line ; dor- 

 sal fin moderate, caudal fin deeply forked, anal fin somewhat elongate, of about 14 rays ; 

 ventrals well developed; pseudobranchiai larg6; gill-rakers varying from short and 

 thick to very long and slender ; air-bladder very large ; stomach horse-shoe shaped, 

 with many — about lOO^pylorio cceoa ; ova small ; species about 40, inhabiting the clear, 

 fresh waters of Northern Europe, Asia, and America, in arctic regions descending to the 

 sea. The group, as here defined, includes a number of sections characterized by minor 

 modifications of ttrnotnre, some ot which have been considered as genera. It seems to 

 ns that the number of distinct species has been overestimated by previous writers, and 

 the dii£culty of distinguishing species is greater, and the geographical range of each 

 one is much wider than has hitherto been generally supposed. The species are highly 

 valued for food ; the coloration is very uniform, bluish above, the sides and below sil- 

 very or olivaceous. 



This genns may be subdivided as follows : 



* Fremaxillaries broad, placed vertically or turned inward, overlapping the tip of the 



lower jaw; the outline of the muzzle, therefore, blnntish or truncate. 



t Preorbital short and very broad ; gill- rakers very short, thick, few in number ; 



supraorbital short, ovate ; maxillary short and rather broad, not reaching to the 



line of the eye ; the small supplementary bone narrow and sharply elliptical ; 



month very small ; the snout more or less produced. {Proaopinm, Milner.) 



QUASRILATERALIS, 



