FISHES—SALMONIDAE—COREGONUS WILLIAMSONI. 
327 
the extremity of the snout. Scales well developed, disposed upon eighteen longitudinal series across the line of the greatest 
depth : nine between the lateral line and the base of the dorsal, and eight between the lateral line and the insertion of the 
ventrals. Bluish lead above ; whitish beneath, with a silvery reflect. 
Syn.— Coregonus williainsoni, Grd. in Proc. Acad. Nat. Sc. Pliilad. VIII, 1856, 13G. 
Two specimens of the female sex have been preserved, the total length of either measuring 
about eleven inches. The body is elongated, rather stout, sub-fusiform in profile; the peduncle 
of the tail well developed. The head is rather small, sub-conical or sub-pyramidal, terminated 
by a truncated snout which protrudes beyond the lower jaw. The mouth is quite small ; the 
maxillar bone being proportionally very broad, but so short that its posterior margin scarcely 
reaches, if at all, a vertical line drawn in front of the orbit. The origin of the dorsal fin is 
nearer the posterior margin of the base of the adipose than the extremity of the snout; its 
upper edge is sub-concave instead of being linear, as exhibited on the accompanying figure. 
The anterior portion of the same fin is higher than its base is long. The adipose is well 
developed, situated immediately opposite the anal fin. The latter is anteriorly deeper than 
long ; its initial ray beiug nearly equidistant between the origin of the ventral fins and the 
insertion of the caudal. The external margin of the anal fin is sub-convex also ; its own base 
entering about eleven times in the total length ; twice in the length of the side of the head. 
The ventrals are inserted opposite the posterior fourth of the base of the dorsal fin ; their 
posterior margin is sub-truncated or rounded off, and when bent backwards their extremities 
are very far from approximating the vent. The pectorals are sub-lanceolated, and, like the 
ventrals, proportionally well developed. The caudal is furcated, shorter than the head, since 
it enters somewhat over six times in the total length. 
Br. Y1I: YII; D 2, 12 + 1; A 2, 12 + 1 ; C 5, 1, 9, 8, 1, 6; V 12 ; P 16. 
The scales are large, deeper than long, with their anterior margin undulating, rounded 
sideways and posteriorly, slightly diminishing in depth. The four sections of the scales are 
limited by a furrow ; the concentric lines are almost entirely obliterated upon the posterior 
section ; no radiating furrows being observed on any of the sections. Eighteen longitudinal 
rows of scales may be counted between the anterior margin of the dorsal and the insertion of 
the ventrals : nine above the lateral line and eight below it. The lateral line itself is perfectly 
straight. Large mucous ducts may be seen on the cheeks extending from the supratympanic 
region to the snout. 
The upper region is bluish grey or lead, whilst the sides and belly are whitish, with a silvery 
reflect all over. 
References to the figures .—Flate LXXYI, lower figure, represents Coregonus tvilliamsoni, 
somewhat reduced in size. Fig. at the upper left corner, a scale from the dorsal region. 
Middle figure, a scale from the lateral line. Fig. at the upper right corner, a scale from 
the abdominal region. 
List of specimens. 
Catal. 
No. 
No. of 
spec. 
Sex and age. 
Locality. 
When coll’d. 
Whence obtained. 
Nat. of spec. 
Collected by—• 
601 
2 
Adult Q 
Des Chutes river, Oregon. 
1855 
Lt. R. S. Williamson. 
Alcoholic .. 
Dr. J. S. Newberry . 
