Jordan and Evermann. Fishes of North America. 463 



very blunt and decurved ; greatest depth of head equal to its length less 

 the opercle. Mouth low, the snout but little projecting, maxillary reach- 

 ing eye in larger specimens, further in the smaller ones ; supplemental 

 bone a crescent ; gill rakers much as in Coregonus wilUamsoni ; scales 

 large. Dull silvery. Head waters of the Columbia River. A small 

 species, not exceeding 8 inches in length, closely related to Coregonus 

 u'HUamsoni, but with larger scales. (Named for Dr. John Merle Coulter, 

 the well-known botanist.) 

 Coregonus coulter ii, EIGEXMANN & EIGENMANN, American Naturalist, November, 1892, 961, 



Kicking Horse River, at Field, British Columbia, one of the head streams of the 



Columbia River. (Typo, No. 44875. Coll. Eigeumann.) 



756. COREGONUS WILLIAMSONI, Girard. 

 (ROCKY MOUNTAIN WHJTEFISH ; "MOUNTAIN HERRING.") 



Head 4| to 5 ; depth 4 to 5 ; eye 4. D. 11 to 14 ; A. 11 to 13 ; scales 8 to 

 10-83 to 87-7 to 10. Body oblong, rather deeper than in Coregonus quadri- 

 lateralis, but little compressed. Head shortish, conic, the profile more 

 abruptly decurved than in the other species. Snout compressed and 

 somewhat pointed at tip, which is entirely below the level of the eye ; pre- 

 orbital broad, width of eye. Maxillary short and very broad, reaching 

 just about to the anterior margin of eye ; therefore, apparently longer 

 than in related species, owing to the shortness of the snout ; supple- 

 mental bone narrow ; maxillary contained 4 times in the length of the 

 head j mandible 3 times. Pectoral 1 in head ; ventral 1| ; longest dorsal 

 ray H. Snout in the males produced, pig-like, in the breeding season. 

 Adipose fin very large, extending behind anal, (rill rakers short and 

 thick, shorter than pupil, about 9 -f- 15. Color bluish above, sides silvery ; 

 breeding males with the under parts white ; all the fins tipped with black, 

 caudal and adipose fins steel-blue. Scales on sides strongly tuberculate 

 in bre'eding males. Length about a foot. Clear streams from the 

 Rocky Mountains to the Pacific, the easternmost records being from Chief 

 Mountain Lake at the head of the Saskatchewan in Montana (as type of 

 Coregonus couesii) ; abundant in the Great Basin, and northwestward on 

 both sides of the Cascade Range; found more often in clear brooks and 

 rivers than in lakes. It readily takes the fly and is an excellent food- 

 fish. (Named for Lieut. R. S. Williamson, in charge of one division of 

 the United States Pacific Railroad explorations.) 



Coregonus u-illiamsoni, GIRARD, Proc. Ac. Nat. Sci. Phila., 1856, 136, Des Chutes River, Ore- 

 gon ; GUNTHER, Cat., vi, 187, 1866 ; JORDAN & GILBERT, Synopsis, 297, 1883 ; B. A. BEAN, 

 in GILBERT & EVERMANN, Bull. U. S. Fish Comm., xiv, 1894, 55, pi. ix, fig. 3. 



Coregonus couesii, MILNER, Rept. U. S. Fish Comm. for 1872-73 (1874), 88, Chief Mountain 

 Lake, Montana ; (Type, No. 14146. Coll. Coues) ; JORDAN & GILBERT, Synopsis, 297, 1883. 



Prosopium couesii, MILNER, iu JORDAN, Man. Vert., Ed. 2, 362, 1878. 



Represented in the Madison and Yellowstone rivers and other tribu- 

 taries of the Upper Missouri by 



766a. COREGONUS WILLIAMSONI CISMONTANUS, Jordan. 



Slenderer, with lower fins. Head 5 in length ; depth 5 to 5i ; pectoral 

 1| in head ; ventral If ; longest dorsal ray 1|. Scales 90. Otherwise like 

 the typical form, (cismontanus, this side of the mountains.) 



