150 
U. S. P. R. R. EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
has a double aperture, one of which being tubular. The branchial apertures are rather wide, 
continuous under the throat; the branchiostegals being six on either side. 
The origin of the dorsal fin corresponds to a vertical line which would intersect the anterior 
rim of the pupil and slightly indexed towards the left side. The rays increase in height 
towards the posterior third of the fin to diminish again posteriorly, all being inclined backwards. 
The anal has the same general structure and appearance, and terminates evenly with the dorsal 
at a short distance from the base of the caudal, its origin corresponding to a line drawn imme¬ 
diately behind the base of the pectorals. The latter are moderate sized and slender, the left 
more so than the right one ; both having dichotomised rays, though less fully developed in the 
left fin. The ventrals are rather small, inserted in advance to the base of the pectorals, and 
extend somewhat beyond the anterior margin of the anal fin and, consequently, overlapping the 
vent. Their middle rays are likewise dichotomised. The caudal fin, which is posteriorly 
rounded or sub-convex, enters five times and a half in the total length ; its rays are simply 
bifurcated without any further subdivision. 
Br. VI: YI; D 74 ; A 59 ; C 3, 1, 6, 6, 1, 3 ; Y 6 ; P 9. 
The scales on the right side are of hut moderate development, longer than deep posteriorly, 
ciliated or pectinated, some of them very conspicuously, others hut slightly ; others still are 
rugose over their entire exposed surface, being quite rough to the touch. Over the head and 
opercular apparatus all the scales are of the rugose type. On the left side all the scales present 
a smooth appearance, and they do not extend over the dorsal, caudal, and anal fins, as is the 
case on the right side. 
The color of the right side is uniform blackish brown ; the left side of a light brown. The 
vertical fins are obsoletely maculated. 
List of specimens. 
Catal. 
No. 
No. of 
spec. 
Age. 
Locality. 
When col¬ 
lected. 
Whence obtained. 
Nature of 
specimens. 
607 
i 
Adult.. 
Cape Flattery, W. T_ 
1856 
Lieut. W. P. Trowbridge_ 
Alcoholic_ 
PLEURONICHTHYS, Girard. 
Gen. Char. —Eyes rather large, situated on the right side. Interocular space very narrow. Head small. Mouth small, its 
gape being oblique, the jaws subequal, and the snout subtruncated. Teeth inconspicuous, occupying both sides of the jaws. 
Origin of dorsal fin placed either in advance of the pupil, or else the entire orbit. Dorsal and anal fins not extending to the 
caudal; latter posteriorly rounded. Scales small, cycloid in structure. Lateral line slightly raised above the pectoral fins, 
otherwise linear. 
Syn .—Pleuronichthys , Grd. in Proc. Acad. Nat. Se. Philad. VII, 1854, 139. 
The body is rather deep, and in that respect resembling somewhat Rhombus , or else combining 
the idea of Rhombus and Solea in its general outline. The smallness of the head and mouth 
are, however, characters which will at once enable a student to discriminate between these 
genera. 
