250 



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



The color is uniform yellowish brown, with a silvery streak along the middle of the flanks. 

 The opercular apparatus and cheek are highly silvery . 



List of specimens. 



LEUCOSOMUS, Heck. 



GEN. CHAR. The body is elongated, sub-fusiform, compressed. The head is stout, conical, either abruptly truncated or 

 tapering off. In either case, the mouth is large, subterminal, and the upper jaw slightly protruding beyond the lower. A 

 small barbel upon the maxillary, near the angle of the mouth. Eyes of medium size. Insertion of ventrals a little in advance 

 of the anterior margin of the dorsal. Caudal furcated. Scales large, somewhat longer than high ; lateral line following the 

 middle of the flanks. Pharyngeal bones stoutish, sickle-shaped ; the inferior branch rather slender, the convexity having a slight 

 expansion tapering off toward&quot; the tip of the upper branch. The teeth are sub-conical, compressed and strongly hooked, of 

 the raptatorial kind, of the hooked type, without grinding surface. They are disposed upon a double row of four and two in 

 the following manner : 2 | 4 4 | 2 ; sometimes 2 | 5 4 | 3, and even 1 | 4 4 | 2. 



STN. Leucosomus, HECK, in Russeg. Reisen, I, H, 1842, 1042. GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 189. 

 Cheilonemus, ED. GRD. in Storer, Hist. Fishes, Mass, in Mem. Amer. Acad. New S. V. 1855, 288. 



The genus Cheilonemus, Bd., is strictly synonymous with Leucosomus ; the latter differs from 

 Semotilus hy the presence of maxillar barbels. 



On a former occasion the genus Leucosomus was altogether misunderstood by me, and from 

 an advice of mine it thus entered into the &quot; History of the Fishes of Massachusetts, by Dr. D. 

 H. Storer.&quot; On framing the genus Leucosomus, Heckel, by inadvertence, applies the name of 

 Cyprinus chrysoleucus , Mitch., to Leuciscus pulcliellus, Storer, as shown by the figures given of 

 its teeth, and the wording of its generical diagnosis. Leucosomus, therefore, is identical with 

 Cheilonemus, and accordingly is the name to be adopted. Cheilonemus was proposed for Leuciscus 

 pulchdlus, and allied species, when it was supposed that Cyprinus chrysoleucus would constitute 

 the type of the genus Leucosomus. But it is now well ascertained that Cyprinus chrysoleucus 

 of Mitchell belongs to Kafinesque s genus Luxilus; and Luxilus has the priority over Leucosomus. 



1. LEUCOSOMUS DISSIMILIS, Gird. 



SPEC. CHAR. Head rather small, sub-conical, constituting the fifth of the total length. Eye large; its diameter entering 

 four times in the length of the side of the head. Gape of mouth somewhat oblique ; posterior extremity of maxillar bone 

 reaching a vertical line drawn in front of the orbit. Anterior margin of dorsal fin nearer the insertion of the caudal than the 

 extremity of the snout. Insertion of ventrals situated in advance of the anterior edge of the dorsal. Greyish brown above, 

 yellowish beneath; flank silvery. Fins greyish olive. 



SVN. Leucosomus dissimilis, GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 189. 



This species may be easily recognized by the small size of the scales of the back compared to 

 those of the flanks. In that respect it approximates certain species of the genus Semotilus. Its 

 head is sub-conical, contained about five times in the total length. The eye is large ; its diame 

 ter being contained four times in the length of the side of the head. The dorsal fin is higher, 

 and the anal deeper, than long. The tips of the ventrals approximate the vent. 



D 1, 8 + 1 ; A 2, 8 + 1 ; C 4, 1, 8, 8, 1, 5 ; V 1, 8 ; P 17. 



