FISHES OF COLORADO 57 



Gila robusia is found only in the Colorado River and its tributaries. Gila 

 elegans Baird and Girard is here considered as synonymous with this species, 

 since intermediate forms and those agreeing with the descriptions of both species 

 were taken from the same station in the Grand River at Grand Junction. In 

 addition, specimens were collected with both the ventral and dorsal portions of the 

 body free from scales, the character given as diagnostic for Gila seminuda Cope 

 and Yarrow. This character seemed fairly constant, although individuals with 

 the ventral region partly scaled were found. Since those individuals naked 

 ventrally and dorsally agreed in other points with Gila robusia, Gila seminuda 

 has been retained as a subspecies of Gila robusia. The specimens examined are 

 listed here under the species proper since intermediate forms were present and this 

 subspecies may not be separable. 



Colorado specimens. — University Museum: Bear River, Lily, Moffatt County, June 30, 1907 

 (230 mm.), E. R. Warren and J. W. Frey, No. 368; Grand River, Grand Junction, August 8, 

 1912 (33 specimens, 40-180 mm.), J. Henderson and M. M. Ellis, No. 369; State Teachers' Col- 

 lege Museum: Delta, A. E. Beardsley; Colorado College Museum: Bear River, Lily, Moffatt County, 

 E. R. Warren (labeled G. seminuda). 



Gila robusta seminuda (Cope and Yarrow) 

 Gila seminuda Cope and Yarrow, Wheeler Survey, Vol. V, p. 666, 1875 (Rio Virgen, Utah). 



Specimens of this subspecies differ from the typical G. robusia in having no 

 scales on the mid-ventral portion of the body as far posterior as the base of the 

 ventrals and no scales on the mid-dorsal region as far back as the middle or last 

 ray of the dorsal fin. 



Genus SEMOTILUS Rafinesque 

 The Fall-fishes 

 Semotilus Rafinesque, Ichthyologia Ohiensis, p. 49, 1820.3 



Moderately large carnivorous Cyprinids; alimentary canal short; mouth 

 large and terminal, very slightly oblique; maxillary barbel present, attached to 

 the upper outer surface of the upper jaw just above the junction of the two 

 jaws, the free portion of the barbel dropping downward and backward into the 

 groove at the junction of the two jaws; lateral line complete and strongly decurved 

 in the pectoral region; length under 20 inches. Species of upper United States 

 and Lower Canada east of the Rocky Mountains; represented in Colorado by 

 the Horned Dace. 



Semotilus atromaculatus (Mitchill) 

 Horned Dace, Creek Chub, the "Chub" (Figs. 25, 26 and 61) 



Cyprinus atromaculatus Mitchill, Amer. Monthly Magazine, Vol. II, p. 324, 1818 (Wallkill 

 River). 



Semotilus atromaculatus (Mitchill) — Jordan, Bull. U.S. Fish Com., Vol. IX, p. 8, 1889 (Den- 

 ver); Jdday, Univ. Colo. Studies, Vol. II, p. 113, 1903 (Boulder; Longmont). 



Semotilus atromaculatus macrocephalus (Girard) — Cockerell, Science, N.S., Vol. XXXIV, 

 p. 615, 1911 (Julesburg). 



