280 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
lateral line is likewise deflexed upon the abdominal region, and nearer the insertion of the 
ventrals than the base of the dorsal. 
The color of the dorsal region and upper surface of the head is blackish brown, whilst the 
sides of the head and the flanks exhibit a metallic yellowish white tint speckled with black. A 
black streak may be observed along the upper region of the flanks, just above the lateral line, 
and partly covering it. The fins are greyish olive ; the ventrals and pectorals being somewhat 
more yellowish or else lighter than the rest. 
References to the fiqures .—Plate LX, fig. 5, represents Ricliardsonius lateralis _, size of life. 
Fig. 6 is a dorsal scale. Fig. 7, a scale from the lateral line. Fig. 8, a scale from the 
abdominal region. 
List of specimens. 
Catal. 
No. 
Cor’g No. 
of teeth. 
No. of 
spec. 
Age. 
Locality. 
When col¬ 
lected. 
Whence obtained. 
Nature of 
specimen. 
Collected by— 
64 
2671 
5 
A.&Y. 
Fort Steilacoom, Puget’s 
Sound, W. T. 
1853 
Gov. I. I. Stevens.. 
Alcoholic. 
Dr. Geo. Suckley... 
LUX1LUS, Rafin. 
Gen. Char. —Body very much compressed, and deepest upon the middle of its length. Head proportionally small and com¬ 
pressed like the body. Mouth small, terminal; when it is shut, the lower jaw fits into the upper one without protrusion of the 
snout ; but when the mouth is partly 4>pen, the lower jaw appears longer than the upper. Eyes quite large. Isthmus small. 
Caudal fin furcated ; insertion of ventrals situated in advance of the anterior margin of the dorsal. Scales large ; lateral line 
forming a very open curve, convex downwards. Pharyngeal bones much stouter superiorly than inferiorly ; a slight expansion 
may be observed upon the convexity of these bones, extending upwards. The teeth are of the bruising kind of the hooked type, 
with a slight hook and a well developed grinding surface, both edges of which being strongly erenated. They are disposed upon 
a single row of five, thus : 5—5. The three uppermost (sometimes the upper two only) stand out in bold relief from the line 
of the bone. 
Syn. — Luxilus , Rafin. Ichth. Ohiens, 1820, 48.— Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 202. 
This is one of the most characteristic genus of North American cyprinoid, and altogether 
misunderstood by Heckel; for, Cyprinus chrysoleucus, Mitch., which he places in his genus Leu- 
cosomus, is generically distinct from Leuciscus pulchellus of Storer, as I have had the opportunity 
to ascertain. The diagnosis given of Leucosomus by its author, and the figures representing the 
pharyngeal dentition, leave no room for doubt. Leucosomus , therefore, is not synonymous with 
Luxilus , but was really established upon a species most intimately related to the one yet unpub¬ 
lished, and which is the type of the genus Cheilonemus. The latter, therefore, must give way 
to Leucosomus , a circumstance unavoidable and very much to be regretted, for it complicates the 
synonymy of both Luxilus and Leucosomus. It will include such species as are congenerical 
with Luxilus chrysocephalus of Rafinesque, and Cyprinus crysoleucas of Mitchill. 
1. LUXILUS OCCIDENTALIS, Grd. 
Spec. Char. —Body rather elongated, sub-fusiform in its outline. Head constituting about the fifth of the total length. 
Snout sub-conical, rather tapering. Gape of the mouth oblique. Posterior extremity of maxillar bone extending to a vertical 
line which would intersect the hind nostril. Eye large and circular ; its diameter entering four times in the length of the side 
of the head. Anterior margin of dorsal fin nearer the insertion of the caudal than the extremity of the snout. Origin of 
ventrals nearer the insertion of the caudal than the extremity of the snout. Anterior edge of anal fin equidistant between 
the isthmus and the tip of the lower lobe of the caudal. Dark greyish brown above ; yellowish beneath, speckled with grey. 
Syn. — Leucosomus occidentalis, B & G. in Proc. Acad. Nat. Sc. Philad. VII, 1854, 137. 
Luxilus occidentalis, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 2U3. 
