300 
U. S. P. R. R, EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
broad when expanded, and, when directed backwards, their extremities remain very far from the 
insertion of the ventrals. 
D 2, 8 + 1; A 2, 8 + 1; C 6, 1, 9, 8, 1, 5 ; V 1, 9 ; P 16. 
The scales, which are of moderate development, are very thin, much deeper than long, sub- 
circular, sub-quadrangular, or undulated upon their periphery. Numerous radiating furrows 
may be observed upon their posterior half, and sometimes also upon the lateral sections, and 
either directed posteriorly from the sides, or else sideways. 
The color of the upper regions is olivaceous, whilst the lower part of the flanks and the belly 
are whitish or yellowish, with a metallic reflect. The fins are unicolor ; the caudal and dorsal, 
greyish ; the others yellowish. 
List of specimens. 
Catal. 
No. 
Cor. No. 
of teeth. 
No. of 
spec. 
Age. 
Locality. 
When 
collected. 
Whence obtained. 
Orig. 
No. 
Nature of 
specimen. 
Collected by— 
204 
937 
i 
i 
Adult. 
San Francisco, Cal. 
1855 
1856 
Lt. R. S.Williamson. 
Dr. W. 0. Ayres... 
21 
Alcoholic. 
... .do.... 
Dr John S. Newberry. 
Dr. W. O. Ayres. 
3. PT Y CHOCHEILUS RAP AX, Grd. 
Plate LXY. 
Spec. Char. —Body elongated, sub-fusiform in profile. Head rather small and tapering forwards, contained four times and 
a half in the total length. Posterior extremity of the maxillar bone extending to a vertical line intersecting the anterior rim 
of the pupil. Eye sub-elliptical ; its diameter entering about eight times in the length of the side of the head. Anterior margin 
of dorsal fin somewhat nearer the fork of the caudal than the extremity of the snout. Fins well developed. Dark brownish 
black above ; whitish beneath. 
Syn. —Ptychocheilws rapax, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 209. 
This is also a large species, differing from P. grandis by a proportionally shorter body, a 
more advanced position of the ventral fins and by much smaller scales on the dorsal region in 
advance of the dorsal. The dorsal fin, compared to its length, is less elevated, although higher 
than long. The inferior limb of the pharyngeal bones is not so long and slender, and there are 
but four teeth upon the main row, instead of five. The teeth and bones are stouter. The 
upper margin of the dorsal fin is nearly linear, somewhat sub-convex. The same is true with 
reference to the anal fin, the anterior margin of which being nearly equidistant between the 
tip of the inferior lobe of the caudal and the base of the pectorals. The ventrals are posteriorly 
rounded, not reaching the vent. The pectorals are likewise broad and rounded off, and their 
extremities, although far from reaching the origin of the ventrals, do, nevertheless, come a 
great deal nearer to it than in P. grandis. 
D 2, 9 + 1; A 2, 8 + 1; C 5, 1, 9, 8, 1, 6; V 1, 9; P 18. 
The scales on the middle of the flanks are of moderate development, and rather small 
elsewhere. They are very thin, deeper than long, sub-circular, irregular in their outline, with 
radiating furrows upon their posterior half, sometimes upon their entire surface. The lateral 
line is nearly median. All the upper surface and sides of the head, as far as a horizontal line 
drawn from the edge of the upper jaw direct to the caudal fin, which line passes below the 
