FISHES — CYPRINIDAE — HYBOGNATHUS ARGYRITIS- 235 



HYBOGNATHUS, Agass. 



Gen. Char. General form elongated, rather slender and compressed. The head is sub-conical, the snout overlapping the 



lower jaw, which is thin and flat, provided upon its symphysis with a small tubercle. The mouth being small, sub-terminal, and 

 directed horizontally forwards ; its angles do not reach the anterior rim of the orbit. The eyes are well developed. There is a 

 narrow isthmus. Anterior ray of dorsal longest. Insertion of ventrals situated posteriorly to the anterior margin of the dorsal. 

 Caudal furcated. The scales are large, deeper than long ; the lateral line following the middle of the flanks. Pharyngeal bones 

 very much bent, with a dilatation upon the convexity, whilst the upper branch is bent inwards, so as to simulate a curve concave 

 from above. The teeth are of the cultriform kind, of the grinding type, very compressed and slightly hooked, and provided 

 with a very narrow grinding surface ; they are disposed upon a single row of four : 4 — 4. 



Sys. —Ilybognathus, Agass. in Amer. Journ. of Sc. 2d ser. XIX, 1855, 2a3.— Grd. in Proc. Acad. Nat. Sc. Philad.Vm, 1856, 181. 



This o-enus is not exclusively limited to the waters of the western States and Territories, for 

 we are already acquainted with a species {H. regius) which inhabits the fresh waters of the 

 Potomac river, and is brought to the Washington market, where it is called "smelt." It 

 exists also in the neighborhood of Baltimore, where it is known under the name of "gudgeon." 

 It grows to a larger size than any of its congeners with which we are so far acquainted. 

 Another species, found in Lake Champlain, is described in the "Natural History of New York" 

 under the name of Luciscus nitidus. — (See Proc. Acad. Nat. Sc. Philad. VIII, 1856, 210.) 



1. HYBOGNATHUS ARGYRITIS, Grd. 

 Plate LIII, Figs. 5—8. 



Spec. Char. — Body sub-fusiform in profile. Head sub-conical, contained five times and a half in the total length. Eye large 

 and sub-circular. Anterior mai-gin of dorsal fin nearer the extremity of the snout than the base of the caudal. Insertion of 

 ventrals equidistant between the two points just alluded to in reference to the dorsal. Caudal fin entering four times and a half 

 in the total length. Scales anteriorly sub-truncated. Olivaceous brown above, yellowish beneath, with a silvery streak along the 

 middle of the flanks. Fins unicolor, greyish olive. 



S»N. — Hybognaihus argyriiis, Grd. in Proc. Acad. Nat. So. Philad. VTH, 1856, 182. 



The largest specimens observed are three inches and a half in total length. This species 

 seems to come nearest to H. nuchalis, Agass., than any of the following ones. The eye, 

 however, is quite large, sub-circular in shape ; its diameter entering a little short of four times 

 in the length of the side of the head. The snout is rather pointed, and the mouth larger than 

 in the species enumerated further on. The branchiostegal rays, three on either side, are very 

 much developed, expanded or flattened though very thin, and overlaping each other. The 

 formula of the fins is as follows : 



Br. Ill : III ; D 2, 8 ; A 2, 8 ; C 7, 1, 9, 8, 1, 6 ; V 1, 8 ; P 14. 



The anterior margin of the dorsal and anal have each two rudimentary rays, and the 

 ventrals, one. The scales are much deeper than long, anteriorly sub-truncated, with radiating 

 furrows upon their posterior section only. 



References to the figures. — Plate LIII, fig. 5, represents Ilybognathus argyritis, size of life. 

 Fig. 6, a scale from the dorsal region. Fig. 7, a scale from the lateral line. Fig. 8, a scale 

 from the abdominal region. 



