FISHES OF COLORADO 23 



ray equalling or slightly exceeding the length of the base of the fin; dorsal rays 

 usually II, sometimes 12, first ray of the dorsal distinctly nearer the tip of the 

 snout than the base of the caudal; pectorals not reaching the ventrals by more 

 than half of their length; ventrals not reaching the anal opening; anal long, 

 reaching the caudal base or beyond, usually with 7 rays, the first being much 

 heavier than the others, especially in breeding males; caudal large, its maximum 

 width being almost equal to the depth of the body; scales 10 or 11, 58-75, 8 to 10, 

 crowded anteriorly. All of the above measurements are taken from medium 

 sized to adult specimens. Small individuals are longer and slimmer than the 

 adults and with the body more uniformly terete. 



A comparison of specimens from different drainages shows a tendency toward 

 a greater number of scales in the lateral line in individuals from the plains streams 

 as opposed to those from the foothill streams, regardless of the river system. 



Lateral Line Scales 

 South Platte: 



Plum Creek near Castle Rock — 60, 60, 61, 62, 6s, 65, 66, 66, 67. 



Boulder Creek, Boulder — 60, 63, 64, 64, 65, 65, 66, 67. 



Julesburg — 64, 65, 67, 68, 6g, 70, 70. 

 Republican: 



Wray— 60, 63, 65, 65, 66, 67, 69, 69, 70, 70, 71, 72, 73, 74, 75, 73. 

 Arkansas: 



Canyon City — 58, 59, 60, 66, 67, 67. 



General color of the dorsal half of the body and head dark greenish or bluish 

 gray to olive-green; margin of the scales outlined with dusky, so that the body 

 especially in the caudal region has a distinctly reticulated pattern; the dark 

 dorsal color disappearing rather abruptly below the lateral line, leaving the 

 lower third of the sides and the ventral parts cream- white; entire body with a 

 metallic reflection; fins hyaline to milky white, the rays, especially those of the 

 caudal, usually opaque white and outlined with dusky; upper surfaces of the 

 pectorals and ventrals somewhat dusky; fins of breeding males, particularly the 

 anal, more or less yellow or orange; under parts of the head yellowish white; lips 

 often with a slightly pinkish cast; top of the head very dark green to almost 

 black. 



The yoimg of this species are much lighter dorsally than the adults, the mid- 

 dorsal region being distinctly mottled. In addition to the adult markings the 

 young also have three rather distinct black or dusky spots along the lateral line, 

 the largest and most prominent being quite near the base of the caudal fin, a 

 second about midway between the base of the caudal and the posterior margin 

 of the operculum, and the third a short distance behind the operculum. These 

 spots are very prominent in individuals about 40 millimeters long, gradually dis- 

 appearing as the fish grows larger. The caudal spot is the last to be lost, per- 

 sisting in quite large and. well-developed individuals. By means of these spots 



