326 Bulletin 47, United States National Museum. 



outline little arched, the profile descending steeply to the lip, nearly 

 even and nowhere concave. Lower jaw included, maxillary reaching 

 anterior border of orbit. Barbels well developed. Dorsal fin inserted in 

 front of ventrals. Olivaceous above, white below; a plumbeous lateral 

 band; fins plain. Length 6 inches. Upper waters of Arkansas River; 

 very abundant in the channels, the most common fish at Pueblo, Colo- 

 rado, (^vffdaj, to thicken ; yva^of, jaw.) 

 CfriiMilhijit phijuhpialhus, CopE, Wheelor Surv., Zoiil., v, 651, 1875, (187(i), Arkansas River, 



Pueblo, Colorado. (Coll. Aiken.) 

 Cotteiiinsph!isi(]iiulhiis, JORDAN & Gilbert, Synopsis, 219, 1883; Jordan, Bull. U. S. Fish Comm., 



ix, 1889, 17. 



54,1. PLATYfiOBIO (JRACILIS (Richardson), 

 (Flat-headed Chub.) 



Head 4J ; depth 4J ; eye 6 in adult. D. 8 ; A. 8 ; scales 6-50-5 ; teeth 

 2, 4-4, 2. Body rather elongate, somewhat compressed, little elevated. 

 Head small and short, its upper surface very broad and depressed, the 

 interorbital width being nearly half length of head ; region behind nape 

 gibbous, so that the anterior profile is more or less concave. Mouth 

 rather large, slightly oblique, the upper lip on level of lower part of 

 eye ; maxillary reaching front of eye ; upper jaw very protractile, lower 

 jaw included. Eye small, rather high up and anterior. Fins rather 

 large; dorsal in advance of middle of body; pectoral falcate, its upper 

 rays elongate; caudal j)eduncle rather stout. Scales large and silvery; 

 lateral line decurved ; 23 scales in front of dorsal. Snout not tuberculate 

 in males, so far as known. Coloration pale ; back olive, sides and below 

 silvery; head mostly white; fins pale; no dark lateral band or caudal 

 spot. Length 12 inches. East slope of the Rocky Mountains, from the 

 Missouri and Yellowstone rivers to the Saskatchewan ; abundant in river 

 channels as far south as Kansas City, not ascending to springs, (gracilis, 

 slender.) 



Cuprimis {Leuciscits) gmci.}i<<, Richardson, Fauna Bor.-.\nier., Fishes, 120, 1830, Saskatchewan 



River, at Carleton House. 

 Pogoniclilhtjscommmun, Girard, Proc. Ac. Nat. Sci. Phila., 18.50, 188, and Pac. R. R. Surv., x, 247, 



1858, Fort Pierre, Fort Union, Milk River, Yellowstone River, Sweetwater 



River. (Type, No. 189, etc. Ooll. Suckley.) 

 Pogouichlhiis (Plalijijohio) gtdoneUus, CoPE, Proc. Ac. Nat. Sci. Phila., 1804, 277, near Bridger's 



Pass; "anal rays 9 ; scales 48." (Coll. Hammond.) 

 Leiicifcus yrnciJiK, Gunther, Cat., vii, 240, 1868. 



Leucosormi!: communis and guloneUus, Gunther, Cat., vii, 207, 2G8, 1808. 

 Platygobio communv<, Gill, Captain Simpson's Expl. Utah, 408, 187G. 

 Platygobio gracilis, Jordan & Gilbert, Synopsis, 220, 1883. 



.544. PLATYGOBIO PALLIDUS, Forbes. 



Head 4; depth 4|; eye 31, 2 in interorbital width ; snout 3f. D.8; A. 

 8; scales 6-55-5; teeth 2, 4-4, 2, hooked and with masticatory surface. 

 Head flat above, the snout overhanging the mouth, which is large and 

 wide, with a maxillary barbel about one-third as long as eye. Mandible 

 reaching vertical through middle of iris. Scales with 22 rows before dor- 

 sal, where they are much smaller than elsewhere. Lateral line straight, 



