70 ITNIVERSITY OF COLORADO STUDIES 



lateral stripe along the lateral line; region from the origin of the pectorals to the 

 base of the anal, below the lateral stripe, with a dusky shading which is usually 

 distinct enough to form a second, incomplete, lateral stripe; all of the markings 

 made up of fine, longitudinal lines which give the whole an engraved appearance. 



2. The same as first type with the addition of numerous strong black spots 

 in and above the lateral stripe, especially posterior to the origin of the dorsal. 



3. All markings wanting or represented by blurred clouds; body rather 

 uniform adobe-color, darker dorsaUy. 



These three color types may represent either extremes of a continuous series 

 of variations in color pattern, i.e., this species may have three modes as regards 

 color and markings; or there may be three or more distinct races of this species 

 the interbreeding of which gives the various recombinations of these color patterns 

 found. This matter is deserving of more attention when larger collections are 

 available. 



Because of the variations found in the specimens examined and the close 

 relation of Agosia yarrowi to Agosia couesii (Yarrow) and Agosia oscula (Girard) 

 a table of variations seen is presented (Table VI) . 



From Table VI it may be seen that the variation in the specimens of Agosia 

 yarrowi examined is such that the three species A. oscula, A. yarrowi and A. 

 couesii as defined by Jordan' are distinguishable only on the basis of scales. 

 Material was not at hand to study the scales of the other two species. 



Colorado specimens. — University Museum: Uncompahgre, Montrose, August 8, 1912 (79 

 specimens, 25-110 mm.), J. Henderson and M. M. Ellis, No. 387; Durango, August 11, 1912 (12 

 specimens, 90-120 mm.), J. Henderson and M. M. Ellis, No. 388; State Teachers' College Museum: 

 Gunnison River, Delta, A. E. Beardsley. 



Subfamily Plagopterinae 

 Genus PLAGOPTERUS Cope 

 Plagopterus Cope, Proc. Amer. Phil. Soc. Phila., p. 301, 1874. 



Body scaleless; dorsal fin with a double dorsal spine, the anterior spine with 

 a groove in which the posterior spine is received; inner margin of the ventral 

 fins adherent to the sides of the body; maxillary barbel present; a single species 

 known only from the Colorado River drainage. 



Plagopterus argentissimus Cope 



Plagopterus argentissimus Cope, Proc. Amer. Phil. Soc. Phila., p. 301, 1874 (San Luis Valley, 

 Colorado) (wrongly ascribed to the Rio Grande). 



In his discussion of this remarkable species Cope, I.e., states that this fish 

 is found in the Colorado Basin in western Colorado. It has subsequently been 

 taken only in the lower Colorado drainage at Ft. Yuma, and is probably not a 

 member of the Colorado fauna. 



'Bull. 47, U.S. Nat. Mus., pp. 309-310, 1896. 



