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U. S P. R. R EXP. AND SURVEYS ZOOLOGY GENERAL REPORT 



of greatest depth of the &quot;body, five above and five below the lateral line, which is nearly median, 

 and at equal distance between the base of the dorsal fin and the insertion of the ventrals. 



The color is dark reddish brown, somewhat lighter beneath than above. A slender blackish 

 streak may be observed along the middle of the flanks. The fins are of a uniform greyish 

 olive tint. 



List of specimens. 



RICHARDSONIUS, Girard. 



GEN. CHAR. The body is very much compressed, sub-fusiform in its outline and deep upon its middle. The head is 

 proportionally small ; the mouth terminal, slightly oblique, constructed upon the same pattern as in Luxilus, though somewhat 

 larger, and unprovided with cirrhi or barbels. The eye is large. Isthmus very narrow. Caudal fin furcated. Insertion of 

 ventrals situated in advance of the anterior margin of the dorsal. Anal fin longer than the dorsal ; its anterior margin situated 

 in advance to the posterior margin of the dorsal, in which respect it differs from Luxilus. Scales deeper than long, posteriorly 

 furrowed. The pharyngeal bones are narrow, with a slight expansion upon their convexity ; the teeth being of the raptatorial 

 kind of the hooked type, strongly hooked, without grinding surface, instead of which a sharp but not crenated ridge. They 

 are disposed upon a double row of four or five and two or three, as follows : 2 | 4 4 | 3, or 2 | 5 5 | 2. 



SYN. Richardsonius, GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 201. 



The present genus bears some resemblance to Squalius, from which it may be distinguished 

 by the smooth edge of the dental ridge and the long anal, together with the peculiar position of 

 the latter in reference to the dorsal. The scales are also smaller and much deeper than long, 

 which is not the case in Squalius. 



1. RICHARDSONIUS BALTEATUS, Grd. 

 PLATE LX, FIGS. 14. 



SPEC. CHAR. Head forming less than the fifth of the total length. Snout sub-conical ; jaws even ; posterior extremity of 

 maxillar bone extending to a vertical line drawn in front of the orbit. Eye large and circular ; its diameter entering three times 

 and a half in the length of the side of the head. Anterior margin of dorsal fin equidistant between the extremity of the snout 

 and the fork of the caudal. Anal fin longer than deep and about as long as the head. Caudal fin constituting about the fourth 

 of the total length. Greyish black above ; silvery white beneath. Fins unicolor. 



SYN. Cyprinus (Jlbramis) balteatus, RICHARDS. Faun. Bor. Amer. Ill, 1836, 301. STORER, Synops. 1846, 160. 

 Richardsonius balteatus, GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 202. 



The greatest depth enters about four times and a half in the total length, the thickness being 

 less than the half of the depth. The head is contained five times and one-third in the total 

 length, of which the caudal fin constitutes about the fourth part. The dorsal fin is higher than 

 long, sub-trapezoid in its outline, the upper margin being nearly linear. The caudal is deeply 

 furcated. The anal is longer than deep and longer than the head itself, and diminishing 

 rapidly in depth posteriorly, its inferior edge being slightly concave, and its anterior margin 

 nearer the isthmus than the tip of the inferior lobe of the caudal. The ventrals are well 

 developed, posteriorly sub-truncated, their tips reaching the vent, which is situated close to the 

 anterior margin of the anal fin. Their origin is nearer the extremity of the snout than the 

 insertion of the caudal. The pectorals are large, elongated, posteriorly rounded, and, when 



