" , '] PROCEEDINGS OF THE NATIONAL MUSEUM. 453 



DESCRIPTION OF THE YELLOW-FINNED TROUT OF TWIN LAKES, 

 COLORADO* 



David Starr Jordan and Barton Warren Evermann. 

 Salmo mykiss macdonaldi subsp. nov. 



Type No. 41730, U. S. National Museum. 



Head, 4 to 4-j 1 ,, in length ; depth, 4£ to 5 ; D. 2, 12. A. 1, 11. B. 10, 

 Scales, 40-184-37, about 125 pores. Length of type, 10 inches; other 

 specimens from 5 to 8 inches. 



Body more elongate and more compressed than usual among the 

 trout; head long, compressed, the snout moderately pointed; mouth 

 rather large, the jaws subequal, the maxillary extending beyond the 

 eye, If to 2 in head; hyoid teeth present, small; opercle longer than 

 usual, its greatest length 4-'- in head, somewhat greater than eye, its 

 posterior margin strongly convex. Eye 5| in head; snout 4£; gill 

 rakers short, x -f 10. 



Scales quite small, and regularly placed. Pectoral tin moderate, If 

 in head ; ventrals 2. Caudal moderately emarginate, the lobes equal. 

 1| in head. 



Color silvery-olive, a broad lemon-yellow shade along the sides ; lower 

 tins bright golden yellow in life; no trace of red, except the usual crim- 

 son dash under the lower jaw, never wanting in Salmo mykiss. 



Body posteriorly and on dorsal and caudal fin profusely speckled with 

 small pepper like spots, smaller than the nostril, and smaller than in 

 any other of the forms of Salmo myJciss. Occasionally these spots are 

 numerous on the anterior part of the body, and even on the head, but 

 usually they are very sparse before the dorsal tin. A round dark dif- 

 fuse blotch on cheek behind eye. 



Pyloric cceca about 40. 



Stomach containing some vegetable matter, bones of suckers, and 

 what appears to be a very large flat white worm, apparently swallowed 

 as part of its food. 



About ten specimens of this species were taken with the fly in the 

 lower Twin Lakes, about 15 miles southwest of Leadville, a beautiful. 

 mountain lake tributary to the Arkansas River. 



Most of the specimens were taken by Mr. George It. Fisher, of Lead- 

 ville, a very enthusiastic and very well informed angler who first made 



* Advance sheets of this paper were distributed January 20, 1890. 

 Proceedings National Museum, Vol. XII— No. 780. 



