230 
U. S. P. R. R. EXP AND SURVEYS—ZOOLOGY-GENERAL REPORT. 
5. DIONDA GRISEA, Grd. 
Plate LII, Figs. 6—10. 
Spec. Char. —Body rather deep upon its middle; greatest depth nearly equal to the length of the head. Head sub-conical and 
slender, contained five times and a half in the total length ; snout topering ; gape of mouth nearly horizontal, its angle being far 
from reaching a vertical line drawn in advance of the orbit. Eye moderate, sub-circular. Caudal fin entering nearly five 
times and a half in the total length. Insertion of ventrals situated somewhat posteriorly to the anterior margin of the dorsal. 
Scales moderate sized, deeper than long. Reddish ash above ; olivaceous beneath ; fins unicolor. 
The species is closely allied to D. plumbed and D. punicea, differing from both of them hy a 
more slender and tapering head ; the snout being, however, blunt as in all the species of the 
same genus. The diameter of the eye enters four times in the length of the side of the head. 
The scales are very different from those of I). punicea , in being deeper than long, in which 
respect they resemble more those of D. plumbea, from which they may be distinguished in being 
less tapering posteriorly. 
The color is of a uniform reddish ash above ; yellowish or olivaceous beneath ; the fins being 
unicolor. 
References to the figures. —Plate LII, fig. 6, represents Dionda grisea, size of life. Fig. 7 is a 
section of the body across the line of greatest depth. Fig. 8, a dorsal scale. Fig. 9, a scale 
from the lateral line. Fig. 10, a scale from the abdominal region. 
List of specimens. 
Catal. 
No. 
No of 
spec. 
Locality. 
When 
collected. 
Whence obtained. 
Orig’l 
No. 
Nature of 
specimen. 
Collected by— 
931 
5 
Twenty miles west of 
Choctaw Agency. 
1853 
Lt. A. W. Whipple 
XVI. 
Alcoholic. 
H. B. Mollhausen 
HYBORHYNCHUS, Agass 
Gen. Char. —Head rather short, upper surface depressed ; snout abruptly truncated and rounded. The mouth is of medium 
size, subterminal, its gape being horizontal, the lower jaw flattened and thin, rounded upon its periphery and slightly overlapped 
by the snout. The angles of the mouth do not reach a vertical line drawn in advance of the orbit. The eyes are large ; the 
isthmus is of moderate width. Anterior ray of dorsal fin shorter than the second. The insertion of the ventrals is situated 
opposite the anterior margin of the dorsal, in advance or posteriorly to it. The caudal is furcated. The scales are large, 
higher than long, with radiating furrows upon their posterior section only ; the lateral line follows the middle of the flanks. 
The pharyrgeal bones are slender, and more so upon the inferior limb, which is longer than the upper and curved backwards 
and sideways, whilst the upper limb is gently curved inwards. The convexity of the same bone is expanded. The teeth are 
of the cultriform kind of the grinding type, very much compressed, slightly hooked, and consequently provided with quite a 
narrow grinding surface. Their disposition is upon a single row of four : 4—4. 
Syn. — Hyborhynchus, Agass. in Amer. Journ. of Sc. 2d ser. XIX, 1855, 222. —Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 
1856, 179. 
The species of this genus, like those of the preceding one, are, generally speaking, of small 
size, not exceeding four inches in total length. H. notatus is the largest of the hitherto known 
species, and we regret that both space and time did not permit its being included in this report. 
