FISHES CYPRINIDAE ORTHODON MICROLEPIDOTUS. 



237 



List of specimens. 



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. 



Svn.Orthodon, GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 182. 



The general aspect of the body reminds us of Gila, but 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. 14. 



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 microlfpidota, 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 sub-concave upon its inferior edge. The ventrals are somewhat larger 

 than the pectorals. 



D 3, 11 ; A 3, 8 + 1 ; C 10, I, 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-tympanic region, bends itself downwards so 

 as to be nearer the abdominal than dorsal outline, becoming again medial along the peduncle 



