6o UNIVERSITY OF COLORADO STUDIES 



fin moderately forked; scales rather small, 12 or 13, 65-75, 7 or 8; lateral line 

 complete, and rather straight, but slightly decurved in the pectoral region; length 

 under 6 inches. 



Color above the lateral line lead gray to rather dark, with a distinct bluish 

 cast; somewhat darker along the mid-dorsal line; abruptly lighter below the lateral 

 line, yellowish shading to almost white ventrally; sides somewhat silvery with a 

 more or less bluish iridescence; fins hyaline, the rays more or less outlined with 

 dusky; scales above the lateral line, and below the lateral line in the pectoral 

 region more or less distinctly outlined with dusky. 



This species, although quite distinct from Semotilus atromaculatus in detail, 

 resembles it in general appearance. The Mountain Dace is a species of the upper 

 Missouri and Platte drainages. 



Colorado specimens. — University Museum: St. Vrain Creek, Longmont, October 17, igo3 

 (no mm.), C. Juday and D. W. Spangler, No. 44; Boulder Creek, Boulder, September and Octo- 

 ber, 1903 (34 specimens, 55-115 mm.), C. Juday and J. Henderson, No. i. 



Genus HYBOPSIS Agassiz 

 The Horny-heads 

 Hybopsis Agassiz, Amer. Journ. Set. Arts, p. 358, 1854. 



Moderately large to small carnivorous Cyprinids; body somewhat elongate 

 and compressed; alimentary canal short; peritoneum pale, dusky or black; 

 mouth large and terminal; a conspicuous maxillary barbel present on each side 

 at the junction of the upper and lower jaws (one species has two barbels on each 

 side); premaxillaries protractile; lateral line complete; species small to medium, 

 length up to 12 inches. A genus of about 20 species distributed over the United 

 States east of the Rocky Mountains; two species have been taken in Colorado. 



a. Maxillary barbels 4; dorsal fin inserted directly above the ventrals . H. tetranemus Gilbert 

 aa. Maxillary barbels 2 ; dorsal fin inserted behind the ventrals . H . kentuckiensis (RaL&aesque) 



Hybopsis tetranemus Gilbert 



FOUR-BARBELED ChUB 



Hybopsis tetranemus Gilbert, Bull. Washburn College Lab., p. 208, 1886 (Elm and Spring 

 Creeks, Medicine Lodge, Kansas); Jordan, Bull. U.S. Fish Com., Vol. IX, p. 17, 1889 (Pueblo). 



A single specimen of this remarkable fish was collected at Pueblo by Jordan 

 in 1889. It has not been recorded from Colorado in any subsequent collection. 

 As it does not occur in any of the collections examined its description is copied 

 below : 



Head 4; depth 5.3; snout 2 . 5 in the head, one-third of it projecting beyond the mouth; eye 

 small, 5 in the head. D.8; A. 8; lateral line 36 to 38; teeth 4-4. Closely resemhling H . aestivalis 

 but with two long barbels at each angle of the mouth, the one pair taking the place of the fleshy 

 prominence seen in gelidus and aestivalis; longest barbel as long as the eye. Head very slender, 

 slenderer than in aestivalis. Dorsal over ventrals, a little nearer tip of snout than caudal. Fins 

 large. Color as in aestivalis, translucent silvery, with irregular, scattered black dots above; median 



