28 UNIVERSITY OF COLORADO STUDIES 



Uncompahgre River, Montrose, August 9, 191 2. 



400 mm., slime, 100 per cent. 



150 mm., slime, 100 per cent. 



100 mm., slime, 50 per cent; a few seeds. Not full. 



170 mm., algae and slime, 100 per cent. 



This species is the common large sucker of the Gila and Colorado rivers, 

 being known only from those drainages. The large individuals of C. latipinnis 

 are of considerable economic importance in supplying a cheap grade of fish for 

 the market. They are taken in considerable numbers from the Grand River at 

 Grand Junction for local use, the Fish Commission allowing the use of the seine 

 by permit for the Flannel-mouth and other species of suckers below the trout 

 streams. Two large females of this species taken at Grand Junction on August 

 7, 191 2, contained well-developed egg-masses. 



Colorado specimens. — University Museum: Gunnison River, Grand Junction, August 7, 

 1912 (13 specimens, 60-200 mm.), J. Henderson and M. M. Ellis, No. 319; Grand River, Grand 

 Junction, August 7, 1912 (5 specimens, 370-450 mm.), J. Henderson and M. M. Ellis, No. 320; 

 Uncompahgre River, Montrose, August 9, 1912 (74 specimens, 30-420 mm.), J. Henderson and 

 M. M. Ellis, No. 321; Slate Teachers' College Museum: Delta, A. E. Beardsley. 



Genus PANTOSTEUS Cope 

 The Mountain Suckers 



Pantosleus Cope, Wheeler Survey, Vol. V, p. 673, 1876. 



Much like Catostomus; fontanelle usually wantmg or at least much reduced 

 in the adult; lower lip not so deeply cleft as in Catostomus; both jaws with well- 

 defined cutting edges. 



The species of this genus are restricted to the streams of the Rocky Mountain 

 region from the Columbia River south into Chihuahua. Two species are found 

 in Colorado, one in the Colorado River drainage and one in the Rio Grande. 



The two quite similar species of this genus found in Colorado may be separated 

 by the number of scales in the lateral line. In most characters their diflferences 

 are those of degree and are apparent only from a series of measurements. 



a. Scales of the lateral line 80 to 92, usually about 85; species of the Rio Grande. 



P. plebius (Baird and Girard) 

 aa. Scales of the lateral line 95 to 115, usually about 100; species of the Colorado River drainage. 



P. delphinus (Cope) 



Pantosteus plebius (Baird and Girard) 



Rio Grande Sucker 



(■; Catostomus plebius Baird and Girard, Proc. Acad. Nat. Sci. Phila., p. 28, 1854 (Rio Mimbres, 

 at tributary of Lake Guzman, Chihuahua). 



Pantosteus plebius (Baird and Girard) — ^Jordan, Bull. U.S. Fish Com., Vol. IX, p. 19, 1889 

 (Del Norte; Alamosa; Rio Conejos 15 miles south of Alamosa); Fowler, Proc. Acad. Nat. Sci. 

 Phila., Vol. LXV, p. 48, 1913 (Watrita Creek). 



Body elongate and terete, but sUghtly compressed in the caudal half; depth 

 4.7St0 5.25in the length to the base of the caudal fin; head rather large, rounded 



