260 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
2. ALBURNELLUS UMBRATILIS, Grd. 
Spec Char. —Head constituting about the fifth of the whole length. Posterior extremity of the maxillary extending to a 
vertical line drawn at the anterior rim of the orbit. Diameter of the eye entering three times and a half in the length of the 
side of the head. Anterior margin of dorsal fin nearer the extremity of the snout than the fork of the caudal. Insertion of 
ventrals nearer the extremity of the snout than the base of the caudal. Pectorals not reaching the insertion of the ventrals. 
Dorsal region greyish brown; flanks silvery grey; belly reddish yellow. 
Syn.— Alburnm umbralilw , Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 193. 
This is a shorter and deeper species, and which might easily he mistaken for a Luxilus, so 
striking is its general resemblance with small specimens of the latter genus. The greatest 
length is about three inches ; the greatest depth being equal to the length of the head, and 
contained five times in the total length. The lateral line, though running along the fourth 
row of scales from the insertion of the ventrals, is mere deflexed upon the abdomen than in A. 
dilectus; the longitudinal rows of scales being fourteen in number. 
D 1, 8 + 1; A 1, 11 + 1 ; C 5, 1, 9, 8, 1, 6; Y 1, 8; P 13. 
The anal fin is nearly as long as deep, and longer than the dorsal; its anterior margin is 
placed a little behind the posterior margin of the dorsal. The tips of the ventrals overlap the 
vent, nearly reaching the anterior margin of the anal. 
The color of the dorsal region is of a greyish brown tint; the sides being of a silvery grey, 
and the belly dull reddish yellow. The fins are olivaceous tinged with greyish. 
List of specimens. 
Catal. 
No. 
Cor. No. 
of teeth. 
No. of 
spec. 
Age. 
Locality. 
When 
collected. 
Whence obtained. 
Nature of 
specimen. 
Collected by— 
73 
2678 
24 
Adt. & Y’g. 
Sugarloaf creek, Ark.. 
1853 
Lt. A. W. Whipple . 
Alcoholic. 
H. B. Molhausen. 
ALBURNOPS, Girard. 
Gen. Char.— Body slender and compressed, protected with large and deciduous scales, which are deeper than long, and 
posteriorly furrowed. Snout rather blunt and thick, overlapping the lower jaw, which is slightly shorter than the upper. Eye 
large. Gill apertures separated beneath by a narrow isthmus. Dorsal fin higher than long. Insertion of ventrals placed 
somewhat behind the anterior margin of the dorsal, else in advance of it. Caudal fin deeply furcated. The pharyngeal bones 
resemble, by their configuration, those of Alburnellus. The teeth themselves are of the prehensile kind of the hooked type, 
with a narrow and sometimes contorted grinding surface. They are disposed upon a double row of two and four: 2 | 4—4 | 2, 
or 1 | 4—4 | 2. 
Syn. — Alburnops, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 194. 
Thus we see that a marked difference between Alburnops and Alburnellus consists in the 
presence of a grinding surface to the teeth in the former, and which is absent in those of the 
latter. 
This genus may furthermore be distinguished from Alburnus and Alburnellus by a smaller 
mouth and by a thickening of the snout, which overlaps slightly the lower jaw, contrary to 
what is the case in Alburnus and Alburnellus. In that respect, Alburnops will remind us of some 
species of Hyborlnynchus. The eye is large ; a very narrow isthmus separates the gill apertures 
beneath. The insertion of the ventrals takes place under the anterior margin of the dorsal fin, 
which resembles that of Alburnus and Alburnellus. 
