1856.] 189 



Color yellowish brown, lighter beneath than above, with a silvery streak along 

 the middle of the flank. 



Specimens of this species were collected in Milk River, an affluent of the 

 upper Missouri, by Dr. Geo. Suckley, under Gov. I. I. Stevens. 



2. GoBio AESTIVALIS. This is quite a characteristic species, differing from all 

 its congeners by a rather compressed body, elevated and arched upon its middle, 

 and taperingsrapidly along the peduncle of the tail. The snout is miich shorter 

 and less obtuse than in G. gelidus ; the eye is larger also, and the position of 

 the ventrals a little more forwards. The scales are larger, too. In coloration 

 we see no marked difference between this species and G. gelidus. 



Caught in the Rio San Juan, near Cadereita, New Leon, by Lieut. D. N. Couch, 

 U. S. A. 



3. GoBio VERNALis. The body is fusiform, thickest anteriorly, tapering pos- 

 teriorly. The head is short, the snout blunt and rounded. The eye is large, 

 its diameter being contained three times and a half in the length of the side of 

 the head. Tlie caudal fin is long and deeply furcated ; it constitutes nearly the 

 fourth of the entire length, whilst the head enters in the latter nearly five times 

 and a half. The color is uniform yellowish brown, with a silvery streak along 

 the middle of the flanks. The opercular apparatus and cheek are highly silvery. 



From Arkansas River, near Fort Smith ; collected by Dr. Geo. G. Shumard. 



Under the head of Luzilus will be found the reasons for transferring the name 

 of 



Leucosomus, Heck. 



to Leuciscits pulchelhcs, instead of Ci/prinus chrysoleiicus. We shall now charac- 

 terize this genus, as it is, henceforth, to stand in the ichthyic system. The body 

 is elongated, subfusiform, compressed. The head is stout, conical, either ab- 

 ruptly truncated or tapering oil'. 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, or immediately 

 under it. Caudal bifurcated. Scales large, a little 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 towards the tip of the upper branch. The teeth are subconical, 

 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 I 44 I 2. 



The genus Cheiloncmus, Bd., is strictly synonymous with iewcoso?K?/; the latter 

 differs from Semotilus by the presence of maxillary barbels. 



1. Leucosomus pulchellus. iewcwcMsjoMMeZZiw, Storer, Rep. 1839, 91. Lm- 

 ciscus argentius, Storer, Rep. 1839, 90. Leucosomus chrysoleuciis, Heck., in Russ. 

 Reise. ii. 1843, 1042, pi. i. Leuciscus storeri, Val., in Cuv. & Yal., Hist. Nat. 

 Poiss. xvii. 1844, 319. Cheilonemus pulcheUus, Grd., in Storer, Fish, of Mass., in 

 Mem. Amer Acad. v. new ser. 1865, 120, pi. xxii., fig. 2. 



Inhabits the fresh waters of New England. 



2. Leucosomus plumbeus. Gobio plumbeus, Aoass., Lake Sup. 1850, 3G6. If 

 at all different from the preceding, this will be a second species of the genus. 



Lake Huron and Lake Superior. 



3. Leucosomus dissimilis. This species will be easilj' recognized by the small 

 size of the scales of the back compared to those of the flanks. In that respect 

 it approximates species of the genus Semotilus. Its head is subconical, contained 

 a little less than four times in the total length. The eye is large, its diameter 

 being contained four times in the length of the side of the head. The color is 



