PILOT FISH. 877 
d. Anal fin elongate of 14 to 17 rays. 5 6 : ONCORBYNCHUS. 59. 
dd. Anal fin short, of 9-11 developed rays. 
e. WVomer flat, its toothed surface plain; teeth on the shaft of the vomer in 
alternating rows or one zigzag row, those on the shaft placed directly 
on the surface of the bone, not on a free crest (posterior vomerine teeth 
sometimes deciduous); species black-spotted. . » SALMO. Ol. 
ee. Vomer boat-shaped, the shaft strongly depressed ; scales very small, about 
200 in the course of the lateral line; species not anadromous. : 
f. Shaft of vomer with a raised crest, bearing strong teeth, the crest pos- 
teriorly free; a baud of stout, recurved teeth on the hyoid bone; 
species gray-spotted. . : 6 5 0 CRISTIVOMER. 52. 
ff. Shaft of vomer without raised crest, entirely toothless; species crim- 
son spotted, the lower fins with marginal bands of black and plain. 
SALVELINUS. 93. 
Genus 49. COREGONUS. | Linnzus. 
Coregonus, LINNUS, Sytema Nature, 1758 (artedi). 
Argyrosomus, AGASSIZ, Lake Superior, 1850 (artedi). 
Prosopium, MILNER, Mss., Jordan, Man. Vert., 2d Ed., 1878 (quadrilateralis). 
Allosomus, JORDAN, Man. Vert., 2d Ed., 1878 (tullibee). 
Type, Salmo (Coregonus) lavaretus, L. 
Etymology, korre, the temples; gonos, angle. 
Body oblong or elongate, compressed ; head more or less conic, compressed, the form 
of the snout varying cunsiderably ; mouth 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 ; pseudobranchiz large; gill-rakers varying from short and 
thick to very long and slender; air-bladder very large; stomach horse-shoe shaped, 
with many—about 100—pyloric caca ; 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, inclades a number of sections characterized by minor 
modifications cf structure, some of which have been considered as genera. It seems to 
us that the number of distinct species has been overestimated by previous writers, and 
the difficulty 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 genus may be subdivided as follows: 
* Premaxillaries broad, placed vertically or turned inward, overlapping the tip of the 
lower jaw; the outline of the muzzle, therefore, bluntish 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 ; 
mouth very small; the snout more or less produced, (Prosopiwm, Milner.) 
QUADRILATERALIS, 
