46 UNIVERSITY OF COLORADO STUDIES 



black hyphen-shaped marks, one on each side of the pore in each scale of the lateral 

 line, forming the middle of the lateral stripe; below the lateral stripe immaculate, 

 white to cream color, often tinged with pink; sides as a whole silvery; top and sides 

 of the head to the level of the lower margin of the eyes dark; rays of the dorsal, 

 of the caudal excepting the most ventral ones, and those of the other fins to some 

 extent, outlined with black; scales above the lateral line outlined with dusky; 

 length 4 inches or less. 



The Sucker-mouthed Minnow is a species of the shallow rapid streams of the 

 western portion of the Mississippi Valley, ranging east of the Rocky Mountains 

 to Illinois and from South Dakota south into southern Texas. Each of the Colo- 

 rado collections of this species was made in clear shallow water with a sand or 

 gravel bottom. This minnow feeds on the small insect larvae and snails found on 

 the stream bed. 



Colorado specimens. — University Museum: St. Vrain Creek, Longmont, October 17, 1903 

 (3 specimens, 95-100 mm.), C. Juday and D. W. Spangler; Lodgepole creek near Ovid, July 20, 

 1912 (16 specimens, 75-95 mm.), J. Henderson and M. M. Ellis, No. 348; Boulder Creek 6 miles 

 east of Boulder, July 25, 1912 (8 specimens, 60-70 mm.), M. M. Ellis, No. 349. 



Genus RICHARDSONIUS Girard 

 The Dace 



Richardsoniiis Girard, Proc. Acad. Nat. Sci. Phila., p. 201, 1856. 



Moderately large to small carnivorous Cyprinids; alimentary canal short; 

 mouth rather large, terminal and slightly oblique; no maxillary barbel; lateral 

 line decurved, usually complete; pharyngeal teeth' in two rows, 2-5-5-2, 1-5-4-1 

 or rarely 1-4-4-1, usually hooked and without grinding surfaces. Most species 

 of this genus are found west of the Rocky Mountains, although the genus is 

 represented in the Mississippi Valley and eastern United States. The species are 

 variable and concerning many little is known. In general the species of Richard- 

 sonius have finer scales and are larger and more elongate than the species of 

 Notropis which, in many respects, they resemble. Two species^ of Richardsonius 

 are known from Colorado. 



'The formulae refer to the number of teeth in the two rows on each side of the head. By 2-5-4-1 is 

 understood s large teeth in one row with 2 smaller ones in front of them on one side of the head, and 4 large 

 teeth with i small one in front of them on the opposite side of the head, i.e., the fish need not be bilaterally 

 symmetrical as regards pharyngeal teeth. To examine these teeth, raise the operculum, insert a small pair 

 of forceps or a hook behind the last gill, seize the pharyngeal bone which lies just behind and below the last 

 gill, and remove the bone. Wash the adhering material from the bone and the teeth may be readily counted 

 with a low-power lens. Care must be used not to break ofi the teeth while removing the bone from the fish 



' Professor A. E. Beardsley reports to the writer the species Richardsonius intermedius (Girard) from 

 Durango, Colorado. Since no specimens of this species have been examined in the present study, it is not 

 listed. If found it may be separated by the smaller scales (the formula being 15, 73-78, 9) from R. pulcltellus, 

 which it closely resembles. R. intermedius is a species of the Gila River. 



