FISHES OF COLORADO 47 



a. Scales quite small, 60 to 70 in the lateral line; size rather large, length up to 12 inches; color 

 bluish silvery, no lateral stripe; species of the Rio Grande. 



R. pulchellus (Baird and Girard) 



aa. Scales larger, 45 to 47 in the lateral line; size small, length 3.5 inches; with a dusky lateral 



stripe; species of the South Platte R. evermanni (Juday) 



Richardsonius pulchellus (Baird and Girard) 

 "Pescadito," Rio Grande Chub 



Gila pulchella Baird and Girard, Proc. Acad. Nat. Sci. Phila., p. 29, 1854 (Rio Mimbres, 

 Lake Guzman, Chihuahua). 



Tigoma nigrescens Girard, Proc. Acad. Nat. Sci. Phila., p. 207, 1856 (Boca Grande and Janos 

 River, Chihuahua). 



Leuciscus pulcher (Girard) — Jordan, Bull. U.S. Fish Com., Vol. IX, p. 20, 1889 (Rio Conejos 

 15 miles south of Alamosa; Del Norte). 



Leuciscus nigrescens (Girard) — Jordan and Evermann, Bull. 47, U.S. Nat. Mus., p. 235, 

 1896 (Rio Grande, Alamosa); Cockerell and Allison, Proc. Biol. Soc. Wash., Vol. XXII, p. 159, 

 1909 (Alamosa). 



Clinostomus pandora Cope, Hayden Survey of Montana for 1S71, p. 475, 1872 (tributaries of 

 the Rio Grande, Sangre de Cristo Pass). 



Body elongate, subterete, not strongly compressed; head conical; depth 

 4 to 4.5, head 3.8 to 4.2 in the length to the base of the caudal; eye large, 4 

 (young) to 5. 5 in the head, about i . 25 in the snout and i. 25 to almost 2 in the 

 interorbital distance; mouth large, slightly if at all oblique; angle of the mouth 

 barely if at all reaching the anterior margin of the eye ; dorsal fin short and rather 

 high, of 8 rays, length of its base less than that of its longest ray, base of the first 

 dorsal ray just behind the level of the ventrals; pectorals long, almost reaching the 

 ventrals; ventrals just reaching the anal opening; anal fin short, of 7 or usually 8 

 rays; caudal peduncle rather narrow, its least depth a little more than 2 in the 

 head; caudal fin rather narrow and deeply forked; scales small, closely imbricated, 

 15 to 17, 60-70, 10 or 11; lateral line complete and strongly decurved in the 

 pectoral region ; size moderately large, length 1 2 inches or less. 



Color above the lateral line dark, iridescent steel blue, mid-dorsal region with 

 a faint dusky stripe; sides of the body and head densely sprinkled with purplish- 

 blue chromatophores ; below the lateral line lighter, shading to silvery white 

 ventrally; dorsal, caudal, and to some extent the anal, fins, sprinkled with dusky; 

 top of the head dark ; axil of the pectorals and ventrals, and body at the base of 

 the anal yellowish to orange-red. 



This species is known only from the Rio Grande drainage, ranging from Colo- 

 rado south into Mexico. It is very abundant and very variable and as a result 

 several species now considered as synonyms of this one have been proposed. 



Colorado specimens. — University Museum: Rio Grande, Alamosa, August, 1889 (no mm.), 



D. S. Jordan, No. 350; San Luis Lake, Costilla County, June 5, 1909 (3 specimens, 170-190 mm.), 



E. R. Warren, No. 351; Rio Grande, Alamosa, July 27, 1912 (251 specimens, 50-200 mm.), M. M. 

 Ellis, No. 352. State Teachers' College Museum: Antonito, Conejos County, A. E. Beardsley; 

 Colorado College Museum: San Luis Lake, Costilla County, June 5, 1909, E. R. Warren. 



