FISHES— CYPRINIDAE—ORTHODON MICROLEPIDOTUS. 
237 
List of specimens. 
Catal. 
No. 
No. of 
spec. 
Locality. 
When col¬ 
lected. 
Whence obtained. 
Nature of 
specimen. 
Collected by— 
89 
5 
Sluice of Arkansas near Fort Makee_ 
1853 
Lt. E. G. Beckwith. 
Alcoholic . 
Lt. Beckwith_ 
ORTHODON, Girard. 
Gen. Char. —Head sub-conical, attenuated towards the snout. The mouth is below the medium size, terminal, oblique, both 
jaws being even; a knob or tubercle upon the symphysis of the lower jaw. Eye of medium size. Isthmus small. Body sub- 
fusiform. The ventrals are inserted behind the anterior margin of the dorsal fin. The caudal is furcated. The scales are 
small, longer than deep; the lateral line is sub-medial, being somewhat depressed along the middle of the abdomen. The 
pharyngeal bones are thin, vertically elevated, or rather broad in the vertical direction, bent as usual, and widening towards the 
upper and inner limb, so as to be broadest there. The lower branch is much narrower. The teeth are of the cultriform kind 
of the grinding type, compressed, lanceolated, erect, very slightly bent inwardly. They are disposed upon a single row of five, 
thus: 5—5, the upper ones being quite raised above the edge of the bone. 
Syn. — Ort/iodon, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856,182 
The general aspect of the body reminds us of Gila, hut the insertion of the ventral fins is 
different. The scales have analogues in other genera. The knob at the symphysis of the lower 
jaw seems to indicate some affinity with Hybognathus, in which the same trait exists. The 
pharyngeal teeth are widely different from all those of the American cyprinoids, so far as 
observed. 
ORTHODON MICROLEPIDOTUS, Grd. 
Plate LIII, Figs. 1—4. 
Spec. Char. —Head moderate, its upper surface flattened and declivous towards the snout, which is obtusely wedge-shaped. 
Mouth moderate, broad; posterior extremity of maxillary extending to a vertical line intersecting the nostril Isthmus very 
narrow. The anterior margin of the dorsal is placed somewhat in advance of the insertion of the ventrals. Peduncle of tail 
slender: base of caudal fin dilated. Pectorals slender; ventrals broad. Greyish brown above, whitish or yellowish beneath. 
Syn. — Gila ir.icrolepidota, Ayres, in Proc. Cal. Acad. Nat. Sc. I, 1855, 21. 
Orthodon microlepidotus, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 182. 
The head constitutes a little more than the fifth of the total length ; and so does the caudal 
fin. The eye is large and sub-circular ; its diameter entering about five times in the length of 
the side of the head. The dorsal fin is somewhat higher anteriorly than long ; its origin is 
nearly equidistant between the extremity of the snout and the insertion of the. caudal, perhaps 
nearer the latter than the former ; its upper margin is sub-concave. The anal is likewise 
deeper than long, and suh-concave upon its inferior edge. The ventrals are somewhat larger 
than the pectorals. 
D 3, 11; A 3, 8 + 1 ; C 10, 1,-9, 8, 1, 10 ; V 1, 10 ; P 19. 
The scales are very small, longer than deep, sub-elliptical in their outline, and furrowed 
upon their entire periphery, exhibiting transverse vacuolae upon the lines of growth of the 
posterior section. The lateral line, from the supra-tympauic region, bends itself downwards so 
as to he nearer the abdominal than dorsal outline, becoming again medial along the peduncle 
