30 UNIVERSITY OF COLORADO STUDIES 



length of the body; dorsal profile sloping, ventral profile almost straight; snout 

 broad and heavy; eye small, its diameter 6 to 9 in the head; interorbital distance 

 about 2. 5 in the head; mouth large, ventral; both jaws with broad horny cutting 

 edges; upper lip large, forming a fleshy hood over the mouth opening; median 

 indentation of the lower lip separated from the margin of the lower jaw by 4 to 7 

 rows of papillae; dorsal fin high, of 10 or 11 rays, base of the first ray nearer 

 tip of snout than to the base or the caudal or rarely midway between them; pec- 

 torals and ventrals as in P. plebius; anal fin large, reaching to the caudal base; 

 scales small in the anterior half of the body increasing in size toward the caudal, 

 95 to 115 in the lateral line. 



General color grayish blue, darker dorsally; scales outlined with dusky, 

 giving a reticulated pattern; dorsal color extending down the sides of the body 

 to the level of the origin of the pectoral ; sides of the body below the lateral line, 

 especially in the anal region, pink to orange-red; pectoral and ventral fins yellow- 

 ish ; a more or less interrupted band of red along the lateral line. 



This species ranges throughout the Colorado River drainage in the headwater 

 streams, being very abundant near the mountains and less so in the lower portions 

 of the system. The stomachs of several specimens from both Montrose and 

 Durango were examined and were found to contain masses of algae and slime. 



Colorado specimens. — University Museum: Uncompahgre, Montrose, August 9, 1912 (283 

 specimens, 50-270 mm.), J- Henderson and M. M. Ellis, No. 323; Rio Florida near Durango, 

 August II, igi2 (90 specimens, 150-250 ram.), J. Henderson and M. M. Ellis, No. 324; State 

 Teachers' College Museum: Delta, A. E. Beardsley. 



Genus XYRAUCHEN Eigenmann and Kirsch 

 The Humpbacked Sucker 

 Xyrauchen Eigenmann and Kirsch, Proc. U.S. Nat. Mus., p. 556, 1888. 



Interneural bones in front of the dorsal fin elevated, supporting a sharp-edged 

 hump; mouth much as in Catostomus. 



The single species of this remarkable genus is found only in the Colorado River 

 and its tributaries. 



Xyrauchen texanus (Abbott) 

 Humpbacked Sucker, Razorbacked Sucker (Figs. 7 and 59) 



Catostomus texanus Abbott, Proc. Acad. Nat. Sci. Phila., p. 473, i860 (Colorado and New 

 rivers). 



Catostomus cypho Lockington, Proc. Acad. Nat. Sci. Phila., p. 237, 1880 (Colorado River at 

 the mouth of the Gila). 



Xyrauchen cypho (Lockington)— Jordan, Bull. U.S. Fish Com., Vol. IX, p. 26, 1889 (Delta, 

 in Gunnison and Uncompahgre rivers). 



Xyrauchen uncompahgre Jordan and Evermann, Bull. U.S. Fish Com., Vol. IX, p. 26, 1889 

 (Delta). 



Xyrauchen texanus (Abbott) — Fowler, Proc. Acad. Nat. Sci. Phila., Vol. LXV, p. S4, 1913- 



